Back with the X - Witness Rachel joining the group
Big Brain Brian - Witness Brain joining the group
Fists of Fury - Kill a mutant with your fists
Kill a zombie - Kill a zombie
Master Craftsman - Fully upgrade a weapon with any status effect
Thought this was a Zombie Game? - Witness Luxo joining the group
Watch this! - Use your first Smart Bomb
A Legion of Zombies - Kill 500 zombies in one level
Can't touch this - Complete a Base quest without taking any damage
Getting to know each other - Complete all character quests
The Collector - Complete 'Dev Card Hunt!'
Touch Base - Complete 'Return to the Military Base'