Full list of all 65 Left 4 Dead 2 achievements worth 1,500 gamerscore. It takes around 20-25 hours to unlock all of the achievements in the base game.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 2 DLC packs containing 15 achievements worth 500 Gamerscore.
Decapitate 200 Infected with a melee weapon.
Kill 100 Common Infected with the chainsaw.
Deploy an ammo upgrade and have your team use it.
Kill 15 Infected with a single grenade launcher blast.
Use a bile bomb on a Tank.
Kill a Spitter before she is able to spit.
Survive the Dead Center campaign.
Survive the Dark Carnival campaign.
Survive the Swamp Fever campaign.
Survive the Hard Rain campaign.
Survive the Parish campaign.
Use every melee weapon to kill Common Infected.
Kill one of each Uncommon Infected.
Kill 10 swampy Mudmen while they are in the water.
Honk the noses of 10 Clowns.
Using a Molotov, burn a Clown leading at least 10 Common Infected.
Prove you are stronger than Moustachio.
As the Charger, bowl through the entire enemy team in a single charge.
Prove you are faster than Moustachio.
As the Charger, grab a Survivor and smash them into the ground for a solid 15 seconds.
As the Jockey, ride a Survivor for more than 12 seconds.
Collect 100 gas cans in Scavenge.
As the Jockey, ride a Survivor and steer them into a Spitter's acid patch.
As the Jockey, ride the Survivors twice in a single life.
Make a Survivor drop a gas can during overtime.
As the Spitter, hit every Survivor with a single acid patch.
Finish a campaign using only melee weapons.
Navigate the impound lot and reach the cemetery safe room without tripping any alarms.
Ignite 50 Common Infected with incendiary ammo.
Navigate the sugar mill and reach the safe room without killing any Witches.
Defend yourself at the crashed airliner without taking damage.
Collect 10 vials of Boomer vomit from infected CEDA agents you have killed.
In a Survival round, get a medal only using melee weapons.
Stop the enemy team from collecting any gas cans during a Scavenge round.
Win a game of Scavenge.
Revive 10 dead Survivors with the defibrillator.
Kill a Jockey within 2 seconds of it jumping on a Survivor.
Survive all campaigns on Expert.
Survive a campaign on Expert skill with Realism mode enabled.
Kill a Tank with melee weapons.
Revive 10 incapacitated Survivors while under the speed-boosting effects of adrenaline.
Kill a Charger with a melee weapon while they are charging.
Rescue Gnome Chompski from the Carnival.
Cross the bridge finale in less than three minutes.
In a Versus round, leave the saferoom to defibrillate a dead teammate.
Form a team and beat an enemy team in 4v4 Versus or Scavenge.
As the Spitter, spit on a Survivor being choked by a Smoker.
As the Charger, grab a Survivor and carry them over 80 feet.
Collect 15 gas cans in a single Scavenge round.
Cause 25 gas can drops as a Special Infected.
Play 6 Mutations.
Using the M60, kill 25 infected without letting go of the trigger.
Collect 10 items dropped by a Fallen Survivor.
Open 5 foot lockers.
Survive The Passing Campaign.
Kill a Tank only with damage from the original Survivors.
Knock off the heads of 18 infected with the golf club.
Play the new Midnight Riders song on a jukebox.
Play 5 full games of Scavenge on The Port.
As the Charger, grab a Survivor and crash them through 8 chairs at the wedding.
Have Bill sacrifice himself for the team.
Complete "The Sacrifice".
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.