Here is the full list of all 12 All Zombies Must Die! achievements.
Complete "Return to the Military Base"
Complete ALL character quests
Complete "Dev Card Hunt"
Kill 500 Zombies in one level
Kill a Mutant with your fists
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
Use your first Smart Bomb
Kill a Zombie