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