Here is the full list of all 12 All Zombies Must Die! achievements.
Kill 500 Zombies in one level
Complete "Dev Card Hunt"
Complete ALL character quests
Complete "Return to the Military Base"
Complete a base quest without taking any damage
Fully upgrade a weapon with any status effect
Witness Luxo joining the group
Witness Brian joining the group
Witness Rachel joining the group
Kill a Mutant with your fists
Use your first Smart Bomb
Kill a Zombie