I've been playing this game off and on since it came out. I've recently gotten back into it, and have played quite a few Impossible games with a variety of races. I think I've gotten a good bit better at the game recently than I had been previously. FYI I tend to play Medium maps, though Large on occasion and sometimes Small. Rarely Huge. I'd say its like 75% Medium games.
1) I'd say that my favorite races for Impossible are Humans and Darloks.
By far Klackons and Psilons are the most powerful races for all of the lower difficulty levels, but I think they fall behind on Impossible. The best thing about playing as Psilons on Impossible is just ensuring that the AI won't have them.
The reason that Humans are Darloks are so good is that their advantage interacts with the AIs, so as the AIs get better, their advantage gets better also. On lower difficulties its easy to outstrip the AIs with either Klackons or Psilons, but on Impossible you can't really do it even with them, so their bonuses aren't nearly as useful. Even with Psilons, unless you just happen to be in a weird game where somehow everyone does horribly, you will fall behind in research. Psilons that aren't leading in research aren't any good.
This is where Darloks come into play. Yes, its true that surviving the early game is difficult, but the advantage of Darloks is that you don't need to grow so big so fast with them, you can stay out of the early voting, or even if you're in it you may still have a chance. The key with Darloks is to start Trade Agreements on the first turn you meet a new race and even engage in frequent Tribute to build relationships. Pay attention to the leader dispositions, don't waste time on Erratic leaders. Stay on their good side if possible, but don't Tribute them.
Darloks are the best at actually keeping up technologically, because their spying bonus is just as strong on Impossible as it is on easier levels. The best maps for them put you toward the middle where you can quickly contact the other races. Focus on Computers and Propulsion to extend range to ensure contact. You want contact with all 5 races ASAP.
Once I get past my initial techs, I'll typically keep 50% to 75% of my research into Computers at all times, and pick one other tech to focus on at a time, typically Propulsion. The other advantage of Darloks is of course they give you the most control over the Diplomacy of the game. Once you get set in and you've gotten at least a few relationships to the point where everyone isn't trying to kill you, you have a lot of power to control the alliances in the game and to keep everyone mad at the leader. As you steal you'll often be able to blame others, so you keep checking the stats and alliances and keep blaming anyone who has an alliance with someone else to keep those alliances broken up.
The early part is a challenge, but once you get past the early part I think Darloks are really strong on Impossible. On lower difficulties they really aren't worth it because its easier to just dominate research, but since being the tech leader is virtually impossible on Impossible that's where Darloks shine. Darloks also make holes in your tech tree essentially irrelevant, so its much less of a concern than other races.
Now as for Humans. I'd say that if you're trying Impossible for the first time or you're struggling with it, then Humans are the way to go for sure. I think overall, if I were to play in a tournament or something, I'd play Humans. By far the best chance of winning on Impossible IMO.
What makes Humans so good on Impossible is a few things, but mainly their Trade Bonus. Of course the good Diplomacy helps. Its nice having everyone like you early on. Like Darloks, Humans also favor a central position with early contact to all the AIs. Other races, like Psilons, Klackons, Sakkra, Meklars, etc. have static bonuses that start to fall behind on Impossible. But for the Humans, their Trade Bonus shines on Impossible because the other AIs have such powerful economies. The Human bonus lets you tap into the AI's power.
What's great about Humans is you can have a relatively small population and still a great economy. I've had Planetary income in the 2K-3K range by early mid game with them while being 3rd or 4th in population. Most of the time, in most games with other races, I'd say that Trade income is unimportant and Trade is mostly just for diplomatic purposes. But for Humans on Impossible Trade income can actually be substantial. Go for the highest trades you can make with all races all the time and regularly upgrade your Trade Agreements. This can actually get you more economic benefit than being Klackon or Meklar. Of course its not immediate like the Klackon bonus, but still.
The bonus to Force Fields is nice too to quickly get Planetary Shields. I like to really pump Paleontology too of course, to try to maximize the use of a smaller number of planets at first. But of course you still can't ignore Computers and you will still need to be able to spy and not fall behind on Computers. Planetary Shields and Computers are key on Impossible no matter what your race.
2) Lots of games are impossible on Impossible. I don't waste too much time on bad maps or impossible situations. If I see, for example, that the Psilons have 12 systems before I've even gotten Sub-light drives or something then I'll just give up such a game because you know its going to be impossible. Run-away Psilons and Meklars on Impossible just aren't worth dealing with. When I start a game if I don't get decent planets (I'm not looking for Rich, etc. just a reasonable spread of non-Poor planets in my home area that I can colonize ) then I'll restart. If within the early game I see that a powerful race is quickly taking all the star systems then I'll restart. I'll admit that I restart more often with Darloks if things go south early with bad diplomacy. Making first contact with Erratic or aggressive leaders can be fatal, especially Klackons.
3) I've grown to really appreciate Computer techs. I used to not pay Computers much mind, but I rely a lot on Spying on Impossible and really there are just so many benefits to Computers. I always favor Robotic Controls over anything and will take that first, then go back and pick-up Battle Computers if needed or just move on. I've grown to REALLY love the Technology Nullifier. I used to not pay any attention to this tech and think it was just a dumb waste, but I've come to see its power on Impossible games.
I'd say that in lower difficulty games its hardly ever needed, and usually its all about the HEF. But on Impossible its not uncommon for opponents to get the HEF, sometimes even before you. Facing large numbers of high-tech ships is not uncommon on Impossible, and I've found that the Technology Nullifier is really the best answer. I'll get into that more in a section on ship designs. But anyway, I'd say that Computers are really important because they do a huge amount to boost your economy with Robotic Controls, the Advanced Space Scanner is pretty key, Battle Computers are of course critical, and Spying is so important on Impossible.
4) Opening moves:
I've refined my opening moves. What I do is probably pretty typical. I send my Colony ship to the best prospect planet right away and will scout other potentials. Usually there is really just 1 or 2 options anyway. As long as I can colonize a reasonable first planet, I'd say pop 40+ right away, then I'll keep playing. Once I colonize then I'll scrap everything except the 2 scouts, design a new 8 BC Scout and cheaper Colony ship. Then I'll set it so I build a Scout in 2 turns, which will eventually turn into every 1 turn. I'll put a Scout on every reachable planet, hopefully getting some Artifact techs in the process. Once I see what I've got, then I'll decide if I need Propulsion at all, and if so whether I need Range 4 or 5. If I can get by with Range 4 I'll prefer that. When I don't need scouts any more then I'll move that production to Research and focus on Propulsion, Planetology and Construction to pop those with the minimum needed research points.
If its possible to expand without Propulsion I'll go for Planetology/Construction first. I'm looking for 80% Emissions from Construction and Eco Restoration from Planetology. Hopefully you get both. Eco Restoration is better, but if I don't get that I'll go for Construction first. If I need Propulsion I'll go for that first, the minimum needed. Not getting either 80% Emissions or Eco Restoration can be really bad, but I've made it work before, even on Impossible, especially with Darloks.
Once I've gotten a Propulsion Range tech + 80% Emissions & Eco Restoration if available, I'll then typically shoot for Robotic Controls III. In the early game I do 100% research into each area at a time, so 100% Propulsion, Construction, Planetology or Computers, as needed. Once I get past Robotic Controls III I'll then typically put research points into everything, but still focus on one thing at a time (unless playing Darloks, when I then will either do 100% Computers or 50-75% Computers and one other tech at a time).
On impossible I tend to keep a disproportionate amount of research into Computers at all times, but may still have more in one other tech at a time as well. Unusually something like at least 10% in Computers with about 30% to 50% into an area of focus and the rest evenly among the other techs. I do try to rush Planetology if possible, which is usually more doable with Humans due to the good relations. Getting to Soil Enrichment ASAP can really be a key. I'll often try to time an offensive push to go along with Soil Enrichment or Terraforming to try and swing myself into a 33% population position to secure the vote. The worst is having the highest population, but not enough to secure the vote. This is a very dangerous position that you don't want to be in for long. Ideally you can go from 3rd to to 1st with a big swing. But of course it doesn't always work out like that.
5) Ship design:
Of course I used to think it was all about the High Energy Focus, but I find a rely on that far less now. I do often find myself in early battles and needed to defend with ships or go on the offensive before getting HEF. I used to prefer Missile Boats, but now I've gotten to really like early Huge ships with Auto Repair. I find that I have a few ship patterns that I tend to rely on.
Early:
1) Mediums with Neutron Pellet Gun + Internal Stabilizer. Typically with Nuclear or Sub-light Drives. Often with Battle Computer III, and using shields depends on what the opponent is using. If they are using lasers and weak missiles then I'll use shields.
2) Large Fighter/Bombers, with the Battle Scanner, the best beam, 1 missile + a few bombs (5-10) (Typically Fusion).
3) Huge Fighter/Bombers. Automated Repair + Battle Scanner, best armor possible, best shield, best computer. Best 1 range beam weapon + 1 or more 5 shot missiles + bombs (typically 10-30).
4) Medium Bombers. Just bombs or Bombs + 1 missile, best possible maneuverability, with Internal Stabilizer, and as defensive as will allow, with possible use of ECM.
For design I always place Beams first, then Bombs and Missiles last. This way if you kill your target with the other stuff the Missiles don't fire and you can fire them at something else. Saves having to turn Missiles off and on so much.
Mid:
1) Huge Fighter/Bombers. Auto-Repair+Repulsor Beam+Battle Scanner: Best of everything, but keep it to just maneuverability level 2. Use Heavy Beam weapons + several 5 shot missiles + bombs. I may go for Anti-Matter Torpedoes here before HEF, which is the only time I ever use Torpedoes.
2) Medium bombers. Just lots of defense, high maneuverability and as many of the best bombs you can carry. Also will typically put a 2 shot missile on as well. So the ideal design is one 2 shot missile + as many bombs as you can get. Then try to build as many of these as needed to 1 shot planets. I may at this point build 2 or 3 different types so they can't all be focused by the planets.
3) Maybe Large Torps. I will sometimes build these depending on what the enemy is doing. If the enemy is using slow ships I may go for Large Torpers with high maneuverability and Torpedoes. This would be something like Sub-light drives or Fusion drives with Internal Stabilizers and Torpedoes. They require a lot of micro management, but you can sometimes just move around with them and avoid everything while hitting with Torpedoes from a distance.
Late:
1) Of course Huge ships with HEF! Typically its Huge Ships with HEF+Auto Repair+Repulsor Beam or Battle Scanner. Auto-Blaster/Gauss-Auto Cannon preferred, but whatever you have that's best. Typically here I drop missiles and just have beam weapons and bombs. Usually something like 20-40 bombs, depending on the type.
2) Bombers. Fast as possible, good defense, possibly Zyro Shields, Bombs + 2 shot Missile. Using Small, Medium or Large depends on the situation and what kind of shields/missiles you're against. Low shields but high missiles = lots of Small Bombers with weaker bombs. High Shields and Low missiles = fewer Large Bombers with better bombers.
3) If needed I'll go for Large ships with Ionic Pulsars. These are lots of fun if the enemy is sending waves of Small or Medium ships. If you can get a Stream Projector+Ionic Pulsar, all the better. Put a Battle Scanner on as well to get the initiative. You may also need to add Battle Computers, even if no weapons, to get initiative. These are best if they move first.
Very Late:
1) Nullifer Armada! Build all ships with Tech Nullifiers, HEF, and possibly Auto Repair or something else. Gauss-Auto Cannon + Mauler Devices, no missiles no bombs.
2) Sometimes I'll build a ship with just Stellar Converters and no HEF to get an additional special on, like maybe a Black Hole Generator if going against Huge stacks of larger ships.
3) A bomber with Subspace Teleporter or, if not available, then enough movement to reach planets on turn 1. Bombs + 2 shot Missiles. Get to the Planet, fire the missiles at a ship, drop bombs. Don't forget the Tech Nullifier!
Massed Tech Nullifiers can turn any enemy fleet into garbage. They even work on Planetary Missile bases so even if they have something like Class XX Planetary Shields and 100 Scatter Pack Xs with enough movement your whole armada can Nullify the Planet before it shoots and they'll barely do damage.
The deal with Tech Nullifiers is that its all or nothing IMO. Either don't bother with them or put them on every ship. A single ship with a Tech Nullifier is almost worthless, especially if you are going against a full fleet. What makes them powerful is being able to get multiple shots off in a turn. With this, even if you have something like 6 stacks of 1 Huge against 6 stacks of 100 Huge, with proper maneuvering and targeting you can win the fight. High movement is good also, at least 4 movement. With 5 movement and initiative you can hit them with Nullifiers on turn 1.
As for when to use Black Hole Generators, I typically go for these when Ionic Pulsars won't work. Basically, Ionic Pulsars are only good vs Small and Medium ships. If you're going against someone with big stacks of Large or Huge ships then you may need Black Hole Generators, but using these can be tricky because they require getting close. So again the Tech Nullfier comes into play. In this scenario I may go with something like:
Huge ship with Black Hole Generators + Tech Nullifier + Subspace teleporter or Displacement Device or Stream Projector or Battle Scanner or Auto Repair, with Stellar Converters and/or possibly bombs.
Toward the end you can typically build ships that are defensive enough to survive anything and ultimately, no matter what they have, Black Hole Generators will wipe them out.
1) I'd say that my favorite races for Impossible are Humans and Darloks.
By far Klackons and Psilons are the most powerful races for all of the lower difficulty levels, but I think they fall behind on Impossible. The best thing about playing as Psilons on Impossible is just ensuring that the AI won't have them.
The reason that Humans are Darloks are so good is that their advantage interacts with the AIs, so as the AIs get better, their advantage gets better also. On lower difficulties its easy to outstrip the AIs with either Klackons or Psilons, but on Impossible you can't really do it even with them, so their bonuses aren't nearly as useful. Even with Psilons, unless you just happen to be in a weird game where somehow everyone does horribly, you will fall behind in research. Psilons that aren't leading in research aren't any good.
This is where Darloks come into play. Yes, its true that surviving the early game is difficult, but the advantage of Darloks is that you don't need to grow so big so fast with them, you can stay out of the early voting, or even if you're in it you may still have a chance. The key with Darloks is to start Trade Agreements on the first turn you meet a new race and even engage in frequent Tribute to build relationships. Pay attention to the leader dispositions, don't waste time on Erratic leaders. Stay on their good side if possible, but don't Tribute them.
Darloks are the best at actually keeping up technologically, because their spying bonus is just as strong on Impossible as it is on easier levels. The best maps for them put you toward the middle where you can quickly contact the other races. Focus on Computers and Propulsion to extend range to ensure contact. You want contact with all 5 races ASAP.
Once I get past my initial techs, I'll typically keep 50% to 75% of my research into Computers at all times, and pick one other tech to focus on at a time, typically Propulsion. The other advantage of Darloks is of course they give you the most control over the Diplomacy of the game. Once you get set in and you've gotten at least a few relationships to the point where everyone isn't trying to kill you, you have a lot of power to control the alliances in the game and to keep everyone mad at the leader. As you steal you'll often be able to blame others, so you keep checking the stats and alliances and keep blaming anyone who has an alliance with someone else to keep those alliances broken up.
The early part is a challenge, but once you get past the early part I think Darloks are really strong on Impossible. On lower difficulties they really aren't worth it because its easier to just dominate research, but since being the tech leader is virtually impossible on Impossible that's where Darloks shine. Darloks also make holes in your tech tree essentially irrelevant, so its much less of a concern than other races.
Now as for Humans. I'd say that if you're trying Impossible for the first time or you're struggling with it, then Humans are the way to go for sure. I think overall, if I were to play in a tournament or something, I'd play Humans. By far the best chance of winning on Impossible IMO.
What makes Humans so good on Impossible is a few things, but mainly their Trade Bonus. Of course the good Diplomacy helps. Its nice having everyone like you early on. Like Darloks, Humans also favor a central position with early contact to all the AIs. Other races, like Psilons, Klackons, Sakkra, Meklars, etc. have static bonuses that start to fall behind on Impossible. But for the Humans, their Trade Bonus shines on Impossible because the other AIs have such powerful economies. The Human bonus lets you tap into the AI's power.
What's great about Humans is you can have a relatively small population and still a great economy. I've had Planetary income in the 2K-3K range by early mid game with them while being 3rd or 4th in population. Most of the time, in most games with other races, I'd say that Trade income is unimportant and Trade is mostly just for diplomatic purposes. But for Humans on Impossible Trade income can actually be substantial. Go for the highest trades you can make with all races all the time and regularly upgrade your Trade Agreements. This can actually get you more economic benefit than being Klackon or Meklar. Of course its not immediate like the Klackon bonus, but still.
The bonus to Force Fields is nice too to quickly get Planetary Shields. I like to really pump Paleontology too of course, to try to maximize the use of a smaller number of planets at first. But of course you still can't ignore Computers and you will still need to be able to spy and not fall behind on Computers. Planetary Shields and Computers are key on Impossible no matter what your race.
2) Lots of games are impossible on Impossible. I don't waste too much time on bad maps or impossible situations. If I see, for example, that the Psilons have 12 systems before I've even gotten Sub-light drives or something then I'll just give up such a game because you know its going to be impossible. Run-away Psilons and Meklars on Impossible just aren't worth dealing with. When I start a game if I don't get decent planets (I'm not looking for Rich, etc. just a reasonable spread of non-Poor planets in my home area that I can colonize ) then I'll restart. If within the early game I see that a powerful race is quickly taking all the star systems then I'll restart. I'll admit that I restart more often with Darloks if things go south early with bad diplomacy. Making first contact with Erratic or aggressive leaders can be fatal, especially Klackons.
3) I've grown to really appreciate Computer techs. I used to not pay Computers much mind, but I rely a lot on Spying on Impossible and really there are just so many benefits to Computers. I always favor Robotic Controls over anything and will take that first, then go back and pick-up Battle Computers if needed or just move on. I've grown to REALLY love the Technology Nullifier. I used to not pay any attention to this tech and think it was just a dumb waste, but I've come to see its power on Impossible games.
I'd say that in lower difficulty games its hardly ever needed, and usually its all about the HEF. But on Impossible its not uncommon for opponents to get the HEF, sometimes even before you. Facing large numbers of high-tech ships is not uncommon on Impossible, and I've found that the Technology Nullifier is really the best answer. I'll get into that more in a section on ship designs. But anyway, I'd say that Computers are really important because they do a huge amount to boost your economy with Robotic Controls, the Advanced Space Scanner is pretty key, Battle Computers are of course critical, and Spying is so important on Impossible.
4) Opening moves:
I've refined my opening moves. What I do is probably pretty typical. I send my Colony ship to the best prospect planet right away and will scout other potentials. Usually there is really just 1 or 2 options anyway. As long as I can colonize a reasonable first planet, I'd say pop 40+ right away, then I'll keep playing. Once I colonize then I'll scrap everything except the 2 scouts, design a new 8 BC Scout and cheaper Colony ship. Then I'll set it so I build a Scout in 2 turns, which will eventually turn into every 1 turn. I'll put a Scout on every reachable planet, hopefully getting some Artifact techs in the process. Once I see what I've got, then I'll decide if I need Propulsion at all, and if so whether I need Range 4 or 5. If I can get by with Range 4 I'll prefer that. When I don't need scouts any more then I'll move that production to Research and focus on Propulsion, Planetology and Construction to pop those with the minimum needed research points.
If its possible to expand without Propulsion I'll go for Planetology/Construction first. I'm looking for 80% Emissions from Construction and Eco Restoration from Planetology. Hopefully you get both. Eco Restoration is better, but if I don't get that I'll go for Construction first. If I need Propulsion I'll go for that first, the minimum needed. Not getting either 80% Emissions or Eco Restoration can be really bad, but I've made it work before, even on Impossible, especially with Darloks.
Once I've gotten a Propulsion Range tech + 80% Emissions & Eco Restoration if available, I'll then typically shoot for Robotic Controls III. In the early game I do 100% research into each area at a time, so 100% Propulsion, Construction, Planetology or Computers, as needed. Once I get past Robotic Controls III I'll then typically put research points into everything, but still focus on one thing at a time (unless playing Darloks, when I then will either do 100% Computers or 50-75% Computers and one other tech at a time).
On impossible I tend to keep a disproportionate amount of research into Computers at all times, but may still have more in one other tech at a time as well. Unusually something like at least 10% in Computers with about 30% to 50% into an area of focus and the rest evenly among the other techs. I do try to rush Planetology if possible, which is usually more doable with Humans due to the good relations. Getting to Soil Enrichment ASAP can really be a key. I'll often try to time an offensive push to go along with Soil Enrichment or Terraforming to try and swing myself into a 33% population position to secure the vote. The worst is having the highest population, but not enough to secure the vote. This is a very dangerous position that you don't want to be in for long. Ideally you can go from 3rd to to 1st with a big swing. But of course it doesn't always work out like that.
5) Ship design:
Of course I used to think it was all about the High Energy Focus, but I find a rely on that far less now. I do often find myself in early battles and needed to defend with ships or go on the offensive before getting HEF. I used to prefer Missile Boats, but now I've gotten to really like early Huge ships with Auto Repair. I find that I have a few ship patterns that I tend to rely on.
Early:
1) Mediums with Neutron Pellet Gun + Internal Stabilizer. Typically with Nuclear or Sub-light Drives. Often with Battle Computer III, and using shields depends on what the opponent is using. If they are using lasers and weak missiles then I'll use shields.
2) Large Fighter/Bombers, with the Battle Scanner, the best beam, 1 missile + a few bombs (5-10) (Typically Fusion).
3) Huge Fighter/Bombers. Automated Repair + Battle Scanner, best armor possible, best shield, best computer. Best 1 range beam weapon + 1 or more 5 shot missiles + bombs (typically 10-30).
4) Medium Bombers. Just bombs or Bombs + 1 missile, best possible maneuverability, with Internal Stabilizer, and as defensive as will allow, with possible use of ECM.
For design I always place Beams first, then Bombs and Missiles last. This way if you kill your target with the other stuff the Missiles don't fire and you can fire them at something else. Saves having to turn Missiles off and on so much.
Mid:
1) Huge Fighter/Bombers. Auto-Repair+Repulsor Beam+Battle Scanner: Best of everything, but keep it to just maneuverability level 2. Use Heavy Beam weapons + several 5 shot missiles + bombs. I may go for Anti-Matter Torpedoes here before HEF, which is the only time I ever use Torpedoes.
2) Medium bombers. Just lots of defense, high maneuverability and as many of the best bombs you can carry. Also will typically put a 2 shot missile on as well. So the ideal design is one 2 shot missile + as many bombs as you can get. Then try to build as many of these as needed to 1 shot planets. I may at this point build 2 or 3 different types so they can't all be focused by the planets.
3) Maybe Large Torps. I will sometimes build these depending on what the enemy is doing. If the enemy is using slow ships I may go for Large Torpers with high maneuverability and Torpedoes. This would be something like Sub-light drives or Fusion drives with Internal Stabilizers and Torpedoes. They require a lot of micro management, but you can sometimes just move around with them and avoid everything while hitting with Torpedoes from a distance.
Late:
1) Of course Huge ships with HEF! Typically its Huge Ships with HEF+Auto Repair+Repulsor Beam or Battle Scanner. Auto-Blaster/Gauss-Auto Cannon preferred, but whatever you have that's best. Typically here I drop missiles and just have beam weapons and bombs. Usually something like 20-40 bombs, depending on the type.
2) Bombers. Fast as possible, good defense, possibly Zyro Shields, Bombs + 2 shot Missile. Using Small, Medium or Large depends on the situation and what kind of shields/missiles you're against. Low shields but high missiles = lots of Small Bombers with weaker bombs. High Shields and Low missiles = fewer Large Bombers with better bombers.
3) If needed I'll go for Large ships with Ionic Pulsars. These are lots of fun if the enemy is sending waves of Small or Medium ships. If you can get a Stream Projector+Ionic Pulsar, all the better. Put a Battle Scanner on as well to get the initiative. You may also need to add Battle Computers, even if no weapons, to get initiative. These are best if they move first.
Very Late:
1) Nullifer Armada! Build all ships with Tech Nullifiers, HEF, and possibly Auto Repair or something else. Gauss-Auto Cannon + Mauler Devices, no missiles no bombs.
2) Sometimes I'll build a ship with just Stellar Converters and no HEF to get an additional special on, like maybe a Black Hole Generator if going against Huge stacks of larger ships.
3) A bomber with Subspace Teleporter or, if not available, then enough movement to reach planets on turn 1. Bombs + 2 shot Missiles. Get to the Planet, fire the missiles at a ship, drop bombs. Don't forget the Tech Nullifier!
Massed Tech Nullifiers can turn any enemy fleet into garbage. They even work on Planetary Missile bases so even if they have something like Class XX Planetary Shields and 100 Scatter Pack Xs with enough movement your whole armada can Nullify the Planet before it shoots and they'll barely do damage.
The deal with Tech Nullifiers is that its all or nothing IMO. Either don't bother with them or put them on every ship. A single ship with a Tech Nullifier is almost worthless, especially if you are going against a full fleet. What makes them powerful is being able to get multiple shots off in a turn. With this, even if you have something like 6 stacks of 1 Huge against 6 stacks of 100 Huge, with proper maneuvering and targeting you can win the fight. High movement is good also, at least 4 movement. With 5 movement and initiative you can hit them with Nullifiers on turn 1.
As for when to use Black Hole Generators, I typically go for these when Ionic Pulsars won't work. Basically, Ionic Pulsars are only good vs Small and Medium ships. If you're going against someone with big stacks of Large or Huge ships then you may need Black Hole Generators, but using these can be tricky because they require getting close. So again the Tech Nullfier comes into play. In this scenario I may go with something like:
Huge ship with Black Hole Generators + Tech Nullifier + Subspace teleporter or Displacement Device or Stream Projector or Battle Scanner or Auto Repair, with Stellar Converters and/or possibly bombs.
Toward the end you can typically build ships that are defensive enough to survive anything and ultimately, no matter what they have, Black Hole Generators will wipe them out.