Here is the full list of all 73 Left 4 Dead achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
No Survivors take damage after contacting the rescue vehicle.
As A Tank hit 20 Survivors with a car in the Crash Course campaign.
Kill all four Survivors on one life as a Tank.
Dole out 5000 total Survivor damage as a Special Infected.
Your team incapacitates three Survivors within five seconds.
Stun a Tank with an explosion in the Crash Course campaign.
As a Special Infected, incap someone who is trying to sacrifice themselves.
Win a Versus campaign of Crash Course.
Kill 53,595 Infected.
Kill 1000 Infected with a mounted machine gun.
Kill 5,359 Infected in the Crash Course campaign.
All Survivors complete a campaign without being vomited on.
Survive a campaign with no Survivors taking damage from Special Infected.
Single-handedly kill a Tank.
Drag a Survivor 100 feet with your tongue as a Smoker.
Cover four Survivors with Boomer bile at once.
Pounce a Survivor for 25 points of damage in the Crash Course campaign.
As an Infected, incap a Survivor who has entered and left a safe room.
Kill a Special Infected with an exploding barrel.
Have all 3 generators running at once in "The Sacrifice" finale.
Constrict two Survivors on one life as a Smoker.
Your team wipes all Survivors after the escape vehicle has opened in Crash Course.
Catch a rare strain of infection, then pass it on to someone else.
Pounce two different Survivors on one life as a Hunter.
Smoker pull a bile-covered Survivor until you hold him during Crash Course.
Revive 50 incapacitated Survivors.
Heal 25 Survivors with a first aid kit.
Heal a fellow Survivor when your own health is below 10.
Kill a Witch with a single headshot.
Shove a Boomer and then kill him without him splashing on anyone.
Earn a Gold medal on every official Survival level.
Earn at least a Silver medal on every official Survival level.
Earn at least a Bronze medal on every official Survival level.
Complete one round of Survival on The Last Stand.
Play an entire campaign with no Survivors taking friendly fire damage.
Survive all campaigns on Expert.
Earn a Gold medal in Survival mode on any official level.
Earn a Silver medal in Survival mode on any official level.
Earn a Bronze medal in Survival mode on any official level.
Finish a campaign without ever using a first aid kit on yourself.
Survive a campaign without being incapacitated.
Survive any campaign on Expert.
Complete "The Sacrifice".
Have Bill sacrifice himself for the team.
Blow up 20 Infected in a single explosion.
Kill a Witch without any Survivor taking damage from her.
Survive an entire campaign using only pistols.
Survive the Blood Harvest campaign.
Survive the Dead Air campaign.
Set 101 Infected on fire.
Survive the Death Toll campaign.
Give pain pills to 10 Survivors.
Kill 10 Smokers as they are pulling helpless Survivors.
Punch a Hunter as he is pouncing.
Survive the Crash Course Campaign.
Restart the generator within 30 seconds of it shutting off.
Protect any Survivor from an attacking Infected 50 times.
Sneak past all Witches in a campaign without disturbing one.
Survive the No Mercy campaign.
Beat a campaign with all 4 Survivors.
Kill a Tank without it dealing any damage to a Survivor.
Light a Tank with a Molotov.
Light a Witch with a Molotov.
Make 100 headshot kills.
Leave a safe room to save an incapped teammate and bring them back safely.
Shove a Hunter off of a pinned and helpless Survivor.
Save another Survivor from a Special Infected while on the ground.
Kill a Smoker who has grabbed you with his tongue.
Kill an Infected with a single blow from behind.
Rescue a Survivor trapped in a closet.
Headshot a Hunter while he's leaping.
Rescue a Survivor from a Smoker's tongue before he takes damage.
You or another Survivor take no damage after being vomited on by a Boomer.