Yeah, you need to kill his lizardmen. You probably need a surprise road to pull that off, and at least two warriors per lizard. Start the turn with warriors who can't reach him, build a road toward him and hit him with a lot of units. The first couple will probably lose, but they should wound him enough for the others to finish the job.
EitB 25 - Perpentach
Occasional mapmaker
Occasional mapmaker