Complete the indicated task to unlock the achievement.

Achievement	How to unlock
Absolute	Kill 250000 zombies.
All 4 Deadly	Get Fire Team, Mirror Image, Wild Bunch and Mantle of Cover then get a ghost pickup.
American Hero	Kill over 5000 zombies in Free Play in one game.
Armory	Stormshield, Regeneration, Armor, Counterblow, Aftershock then survive 10 minutes.
Arms Dealer	Get at least one kill with every non-melee weapon in one game.
Back2Back	Remain within reaching distance of your coop player while both of you not taking any damage for 30 seconds.
Blockade	Survive for 15 attack waves in Barricade Mode.
Boss Hunter	Friendly Fire, Mano a Mano and Boss Power then kill 5 bosses in one game.
Bouncer	Survive 5 waves in Barricade Mode without the lower sentry guns having to fire a single shot.
Breather	Pick up health then survive 25 seconds in Free Play without damage or firing a single shot.
Butcher	Get 10 zombies sucked into one Meat Grinder.
Chain Reaction	Pick up Friendly Fire and use a Zombie Bomber's explosion to kill two more nearby bombers.
Coldblooded	Survive for three attack waves in Barricade Mode without moving.
Collector	Collect at least 40 perks in a single game.
Cover	Kill 25 zombies while remaining inside one Turbine area.
Death Cheat	Survive 5 minutes with health staying below 25%.
Demolitions Expert	Get Shrapnel and Remote Detonator then use 10 grenades in one game.
Dive Bomber	In one game dive jump through 100 Zombie Bombers causing them to detonate themselves.
Efficiency	Kill at least 10 zombies with one grenade.
Execution	Kill at least 250 zombies using sentry guns.
Explosive Irony	Deal the killing blow to a Grenade Zombie with a grenade.
Fire Chief	Burn 800 zombies with the Flame Thrower.
Flak Jacket	Get hurt by and survive 10 Zombie Bomber explosions in one game.
Flatliner	Bring yourself back to full health after nearly dying with Last Breath.
Fortress	Survive for 10 attack waves in Barricade Mode.
Free Man	Finish off a boss zombie with the crowbar.
Grenadier	Shrapnel and Midair Trigger then get 500 kills with the grenade launcher.
Guardian	Complete the Point Defense mission.
Gut Buster	Decapitate 100 Big Boy zombies in a single game.
Horde	Kill 50 zombies within a ten second period.
Itemizer	Pick up 250 powerups or items in one game.
Ladies First	Kill 5 female zombies in one streak without killing a single male.
Lockdown	Reach wave 2 in warehouse barricade without any zombie breaching the fence perimeter.
Magnet	Collect 10 zombie-attracting Rammers in one game.
Moths to the Flame	Set fire to 50 zombies that are being attracted by a Rammer in a single game.
No Guns	Kill 500 zombies with a melee weapon.
Not Addicted	Pick up 10 health power-ups in one game when your health is at 100%.
One Trick Killer	Survive for 30 minutes in a game by only picking one perk and by only picking up a maximum of one new weapon.
Payback	Take 2500 zombies down with you using the Vengeance perk.
Resurrector	Revive you coop player 3 times in one game.
Rhylos' 50	Get 50 achievements, then kill 50 bosses and score 50 million in one game.
Right-Hand Man	Get ghosts to kill 25 zombies in one streak while killing none yourself.
Runner	Run a marathon length 26 miles/42 kms.
Speedkiller	Kill any boss within 30 seconds of him appearing.
Stopping Power	Kill 150 running zombies in a single game.
Stronghold	Kill 100 zombies in Survival Mode without moving from start of game.
Survivor	Survive for more than 2 minutes in survival mode.
TeleFrag	Perform 20 grenade teleports.
Thinning The Horde	Kill 1,000,000 zombies.
Ton Of Bullets	Fire 10000 bullets while not receiving any zombie damage.
Too Close For Comfort	Kill 25 Bombers with a Steam Hammer in one game while staying outside their explosion range.
Tough Guy	Kill 1000 zombies in any single game without ever picking a perk.
Unseen	While cloaked, kill 250 zombies in one game.
Untouchable	Complete any mission without taking any zombie damage..
Victor	Kill all zombie boss types.
Weapons Expert	Get Dexterity, Intensity, Accuracy, Heavy Ammo, Improved Loadout then get 1000 kills.
Well Supplied	Explode 3 propane gas tanks within a 10-second period.
Winner	Complete all the story missions.