As the Boomer, vomit on a Survivor without having direct line of sight with them.
Play 6 Mutations.
Cause 25 gas can drops as a Special Infected.
Make a Survivor drop a gas can during overtime.
Earn a gold medal on any official survival map.
Survive for 10 minutes on any official map in Versus Survival.
Earn a silver medal on any official survival map.
Earn a bronze medal on any official Survival map.
Revive an incapacitated teammate while a Tank is nearby.
Revive 10 incapacitated Survivors while under the speed-boosting effects of adrenaline.
If you are reading this achievement, Gabe Newell has successfully launched Gnome Chompski into space.
Survive The Passing Campaign.
Plays games with free weekend players and helps them survive a campaign.
Complete "The Sacrifice".
Open 5 foot lockers.
As the Spitter, hit every Survivor with a single acid patch.
Collect 10 vials of Boomer vomit from infected CEDA agents you have killed.
Use a bile bomb on a Tank.
Kill 15 Infected with a single grenade launcher blast.
Survive the Dead Center campaign.
Ignite 50 Common Infected with incendiary ammo.
Play the new Midnight Riders song on a jukebox.
Kill a Tank with melee weapons.
Using the M60, kill 25 infected without letting go of the trigger.
Navigate the impound lot and reach the cemetery safe room without tripping any alarms.
Kill 100 Common Infected with the chainsaw.
Kill one of each Uncommon Infected.
Kill a Jockey within 2 seconds of it jumping on a Survivor.
Kill a Spitter before she is able to spit.
As the Charger, grab a Survivor and smash them into the ground for a solid 15 seconds.
Deploy an ammo upgrade and have your team use it.
Collect three gifts dropped by Special Infected in Versus Mode.
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.
Win a game of Scavenge.
As the Jockey, ride a Survivor for more than 12 seconds.
Stop the enemy team from collecting any gas cans during a Scavenge round.
Honk the noses of 10 Clowns.
Using a Molotov, burn a Clown leading at least 10 Common Infected.
Kill a Charger with a melee weapon while they are charging.
Decapitate 200 Infected with a melee weapon.
Kill 10 swampy Mudmen while they are in the water.
Revive 10 dead Survivors with the defibrillator.
Use every melee weapon to kill Common Infected.
Survive the Dark Carnival campaign.
Survive the Swamp Fever campaign.
Survive the Hard Rain campaign.
Survive the Parish campaign.
Navigate the sugar mill and reach the safe room without killing any Witches.
Collect 15 gas cans in a single Scavenge round.
Prove you are faster than Moustachio.
Collect 10 items dropped by a Fallen Survivor.
Knock off the heads of 18 infected with the golf club.
Kill a Tank only with damage from the original Survivors.
Have Bill sacrifice himself for the team.
Survive the Cold Stream campaign on any difficulty.
Finish a campaign using only melee weapons.
In a Versus round, leave the saferoom to defibrillate a dead teammate.
Survive all campaigns on Expert.
Survive a campaign on Expert skill with Realism mode enabled.
Form a team and beat an enemy team in 4v4 Versus or Scavenge.
Cross the bridge finale in less than three minutes.
Rescue Gnome Chompski from the Carnival.
Defend yourself at the crashed airliner without taking damage.
As the Spitter, spit on a Survivor being choked by a Smoker.
As the Charger, bowl through the entire enemy team in a single charge.
As the Charger, grab a Survivor and carry them over 80 feet.
In a Survival round, get a medal only using melee weapons.
Collect 100 gas cans in Scavenge.
Prove you are stronger than Moustachio.
As the Charger, grab a Survivor and crash them through 8 chairs at the wedding.
Play 5 full games of Scavenge on The Port.
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.
Play a Versus game on Dead Air from start to finish.
Spread cheer by helping a free holiday player survive a campaign.
Survive The Last Stand campaign on any difficulty.
Survive The Last Stand campaign on Expert Realism.
Find the golden crowbars hidden in the Left 4 Dead 1 survival maps.
As the Spitter, spit on a Survivor who is pinned by a Charger.
As the Spitter, spit on a Survivor who is pinned by a Hunter.
Destroy 20 gascans as the Spitter.
Instantly kill a Survivor as the Charger.
Rescue three Survivors from a single rescue closet.
With a sharp melee weapon, cut a Smoker's tongue before he ensnares you.
Kill a pouncing Hunter with a shotgun.
Destroy a Tank's rock in mid-air.
Kill the Witch bride with a single shotgun blast on expert difficulty.
As the Hunter, land a 25 damage pounce.
Kill 20 Jockeys with the shovel or pitchfork.
Kill 53,599 infected. You made sure the dead won't rise anymore!
Escape Liberty Mall's Atrium before the first Tank appears
Discover the hidden room in the Last Stand campaign
Earn a bronze medal on every official survival map
Earn a silver medal on every official survival map.
Earn a gold medal on every official survival map.
Survive for 30 minutes on any official survival map.
Kill a Witch using only a sharp melee weapon, without anyone getting incapacitated or killed.
On the concert finale, survive until the helicopter arrives without leaving the stage
Complete The Last Stand campaign in 13 minutes or less, without any Survivors dying.
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