Full list of all 21 #KILLALLZOMBIES achievements worth 1,000 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Xbox One.
Killed 500,000 zombies.
Stayed alive at least 60 minutes.
Killed at least 1,000 zombies with a Pepyaka gun.
Killed at least 1,000 zombies with a Plasma gun.
Exploded at least 100 cars in one session.
Racked up to 30 level.
Scored 10,000,000 experience points in a single session.
Killed at least 1,000 zombies with an M-60.
Killed at least 1,000 zombies with a Spread gun.
Killed at least 1,000 zombies with a Volcano machine gun.
Killed at least 1,000 zombies with an M-16.
Killed at least 1,000 zombies with a crossbow.
Killed the first Undead Boss.
Killed at least 1,000 zombies with a flare gun.
Killed at least 1,000 zombies with an Uzi.
Killed at least 1,000 zombies with a revolver.
Killed at least 1,000 zombies with a pistol.
Didn't shoot for whole six minutes and survived.
Killed at least 1,000 zombies with a shotgun.
Performed a rampage attack.
Used melee attack 100 times in one session.