Hi! How exactly do they need to die? I tried grabbing catjeet provisioners from my market and casting a spell to kill them. But it does not count towards the achievement.
Do they have to join your village and then die?

SOLUTION: In case anyone is looking for a shortcut.

Start a village. Hire 6 or more catjeet. Then let monsters plunge your village and kill everybody.

After day 35 and 200+ villagers, I just had to destroy my defenses and wait a couple of days. Then got the achievement.