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