Left 4 Dead achievements

Kill 10 Smokers as they are pulling helpless Survivors.

Set 101 Infected on fire.

Beat a campaign with all 4 Survivors.

Shove a Hunter off of a pinned and helpless Survivor.

Rescue a Survivor trapped in a closet.

Protect any Survivor from an attacking Infected 50 times.

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.

Kill a Tank without it dealing any damage to a Survivor.

Make 100 headshot kills.

Free yourself from a Smoker who has grabbed you with his tongue.