Left 4 Dead 2 achievements

Plays games with free weekend players and helps them survive a campaign.

Destroy a Tank's rock in mid-air.

In a Survival round, get a medal only using melee weapons.

Kill a pouncing Hunter with a shotgun.

Revive 10 incapacitated Survivors while under the speed-boosting effects of adrenaline.

Survive The Last Stand campaign on any difficulty.

Play a Versus game on Dead Air from start to finish.

Play 6 Mutations.

Defend yourself at the crashed airliner without taking damage.

Revive 10 dead Survivors with the defibrillator.

Make a Survivor drop a gas can during overtime.

Kill a Special Infected with an exploding barrel.