Full list of all 65 Left 4 Dead achievements worth 1,500 gamerscore. It takes around 40-50 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 3 DLC packs containing 15 achievements worth 500 Gamerscore.
Kill 1000 Infected with a mounted machine gun.
Survive all campaigns on Expert.
As an Infected, incap a Survivor who has entered and left a safe room.
Kill all four Survivors in one life while playing as a Tank.
No Survivors take damage after contacting the rescue vehicle.
Survive the Blood Harvest campaign.
Survive a campaign with no Survivors taking damage from Special Infected.
Heal 25 Survivors with a first aid kit.
Play an entire campaign with no Survivors taking friendly fire damage.
Survive any campaign on Expert.
All Survivors complete a campaign without being vomited on.
Finish a campaign without ever being healed.
Headshot a Hunter while he's leaping.
Heal a fellow Survivor when your own health is below 10.
Survive a campaign without being incapacitated.
Survive the Dead Air campaign.
Survive the Death Toll campaign.
Leave a safe room to save an incapped teammate and bring them back safely.
Single-handedly kill a Tank.
Sneak past all Witches in a campaign without disturbing one.
Survive an entire campaign using only pistols.
Revive 50 incapacitated Survivors.
Blow up 20 Infected in a single explosion.
Survive the No Mercy campaign.
Beat a campaign with all 4 Survivors.
Give pain pills to 10 Survivors.
Kill a Witch without any Survivor taking damage from her.
Kill a Witch with a single headshot.
Set 101 Infected on fire.
Light a Tank with a Molotov.
Cover four Survivors with Boomer bile at once.
Dole out 5000 total Survivor damage as a Special Infected.
Drag a Survivor 100 feet with your tongue.
Constrict two Survivors in one life as a Smoker.
Punch a Hunter as he is pouncing.
Kill a Tank without it dealing any damage to a Survivor.
Light a Witch with a Molotov.
Kill an Infected with a single blow from behind.
Shove a Boomer and then kill him without him splashing on anyone.
Pounce two different Survivors in one life as a Hunter.
Shove a Hunter off of a pinned and helpless Survivor.
Make 100 headshot kills.
Rescue a Survivor trapped in a closet.
Kill 10 Smokers as they are pulling helpless Survivors.
Save another Survivor from a Special Infected while on the ground.
Protect any Survivor from an attacking Infected 50 times.
You or another Survivor take no damage after being vomited on by a Boomer.
Rescue a Survivor from a Smoker's tongue before he takes damage.
Free yourself from a Smoker who has grabbed you with his tongue.
Kill 53,595 Infected.
Survive the Crash Course Campaign.
Restart the generator within 30 seconds of it shutting off in the Crash Course campaign.
Kill 5,359 Infected in the Crash Course campaign.
Win a Versus campaign of Crash Course.
Your team wipes all Survivors after the escape vehicle has opened in Crash Course.
Pounce a Survivor for 25 points of damage in the Crash Course campaign.
Smoker pull a bile-covered Survivor until you hold him during Crash Course.
Stun a Tank with an explosion in the Crash Course campaign.
Your team incapacitates three Survivors within five seconds in the Crash Course campaign.
As a Tank hit 20 Survivors with a car in the Crash Course campaign.
Complete "The Sacrifice".
Have Bill sacrifice himself for the team.
Kill a Special Infected with an exploding barrel.
Have all 3 generators running at once in "The Sacrifice" finale.
As a Special Infected, incap someone who is trying to sacrifice themselves.