Complete the following task to unlock the corresponding achievement.

Achievement	How to unlock
101 Cremations	Set 101 Infected on fire.
Akimbo Assassin	Survive a campaign firing no guns other than pistols.
All 4 Dead	Kill all four Survivors on one life as a Tank.
Back 2 Help	Leave a safe room to save an incapped teammate and bring them back
Barf Bagged	Cover four Survivors with Boomer bile at once.
Big Drag	Drag a Survivor x distance with your tongue.
Blind Luck	You or another Survivor take no damage after being vomited on by a Boomer.
Brain Salad	Make 100 headshot kills.
Burn the Witch	Light a Witch with a Molotov.
Chain Smoker	Constrict two Survivors on one life as a Smoker.
Clean Kill	Shove a Boomer and then kill him without him splashing on anyone.
Cr0wnd	Kill a Witch with a single headshot.
Dead Baron	Survive the Dead Air campaign.
Dead Giveaway	Heal a fellow Survivor when your own health is below 10.
Dead Stop	Punch a Hunter as he is pouncing.
Dead Wreckening	Dole out 5000 total Survivor damage as a Special Infected.
Do Not Disturb	Sneak past all Witches in a campaign without disturbing one.
Double Jump	Pounce two different Survivors on one life as a Hunter.
Drag and Drop	Rescue a Survivor from a Smoker's tongue before he takes damage.
Field Medic	Heal 25 Survivors with a first aid kit.
Grim Reaper	Survive the Blood Harvest campaign.
Ground Cover	Save another Survivor from a Special Infected while on the ground.
Helping Hand	Revive 50 incapacitated Survivors.
Hero Closet	Rescue a Survivor trapped in a closet.
Hunter Punter	Shove a Hunter off of a pinned and helpless Survivor.
Jump Shot	Headshot a Hunter while he's leaping.
Lamb 2 Slaughter	Incapacitate a Survivor after he has entered and exited a safe room.
Man vs Tank	Single-handedly kill a Tank.
Mercy Killer	Survive the No Mercy campaign.
My Bodyguard	Protect any Survivor from an attacking Infected 50 times.
No Smoking Section	Kill 10 Smokers as they are pulling helpless Survivors.
No-One Left Behind	Beat a campaign with all 4 Survivors.
Nothing Special	Survive a campaign with no Survivors taking damage from Specials.
Pharm-assist	Give pain pills to 10 Survivors.
Pyrotechnician	Blow up 20 Infected in a single explosion.
Red Mist	Kill 1000 Infected with a mounted machine gun.
Safety First	Play through a campaign with no Survivors taking friendly fire damage.
Spinal Tap	Kill an Infected with a single blow from behind.
Stand Tall	Survive a campaign without being incapacitated.
Stomach Upset	All Survivors complete a campaign without being vomited on.
Tankbusters	Kill a Tank without it dealing any damage to a Survivor.
Toll Collector	Survive the Death Toll campaign.
Tongue Twister	Kill a Smoker who has grabbed you with his tongue.
Towering Inferno	Light a Tank with a Molotov.
Unbreakable	Beat a campaign without ever using a first aid kit on yourself.
Untouchables	No Survivors take damage after contacting the rescue vehicle.
What Are You Trying To Prove?	Survive all campaigns on Impossible.
Witch Hunter	Kill a Witch without any Survivor taking damage from her.
Zombicidal Maniac	Survive any campaign on Impossible.
Zombie Genocidest	Kill 53,595 Infected.