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