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