Accumulate 25000 heal points as a Medic.
Accumulate 1000 total kills.
Win 20 games.
Play a complete round with every class.
Win 2Fort with a shutout.
Get five revenge kills.
Get 25 headshots as a Sniper.
Play a complete game on every map.
Set five enemies on fire in 30 seconds.
Accumulate 10 turret kills with a single turret.
Win Well in 5 minutes or less.
Win Hydro without giving up a capture.
Successfully defend Dustbowl without giving up a capture.
Trick an opposing medic into healing you.
Successfully defend Gravel Pit without giving up a capture.
Get five kills in a row without dying.
Play in a game with seven or more players from your friends list.
Earn bronze medals on all Portal challenges.
Earn silver medals on all Portal challenges.
Earn gold medals on all Portal challenges.
Use flares to light 15 zombies on fire.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Find all lambda caches in Half-Life 2.
Kill five enemies with a Manhack.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Send the garden gnome into space.
Squish every antlion grub in Episode Two.
Kill all of the snipers in City 17.
Kill 3 enemies using the crane.
Play through Ravenholm using only the Gravity Gun.
Continue playing to unlock this secret achievement.
Detach security cameras from the walls.
Kill a Hunter with its own flechettes.
Save all buildings outside the missile silo from destruction.
Beat DOG in a race to the White Forest base.
Defeat the chopper in Episode Two without any misses.
Find and break every web cache in Episode Two.
Beat Episode One firing exactly one bullet. Grenade, crowbar, rocket, and Gravgun kills are okay!
Don't let any citizens die when escorting them to the escape train.
Kill a Combine soldier with his own grenade.
Contain the Citadel core without killing any stalkers.
Jump 300 feet.
Kill five barnacles with one barrel.
Find every radar cache in chapter Under The Radar.
Unlock the rocket launcher lambda cache in chapter Under The Radar.
Run over 20 enemies with the car in Episode Two.
Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.
Kill an acid antlion worker.
Escape City 17 with Alyx.
Destroy the gunship in the hospital attic.
Help Alyx snipe 30 enemies in Episode One.
Use the cars to squash 15 antlions in Episode One.
Survive long enough to get on the parking garage elevator.
Steal a Zombine's grenade.
Contain the Citadel core.
Make it to the bottom of the Citadel's main elevator shaft in one piece.
Use DOG's ball to make a basket in Eli's scrapyard.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Break the mini-teleporter in Kleiner's lab.
Kill an Elite Soldier with his own energy ball.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Survive the rooftop strider battle in the ruins of City 17.
Kill five enemies with the same energy ball.
Shut down the supression device by disabling its generators.
Survive the generator plaza standoff in chapter Anticitizen One.
Get through the toxic tunnel under City 17 in Half-Life 2.
Kill an enemy by planting a hopper mine.
Gain command of a squad of rebels in the uprising.
Survive the second turret standoff in Nova Prospekt.
Kill an enemy with a toilet.
Destroy six gunships in Half-Life 2.
Use the antlions to kill 50 enemies.
Pin a soldier to the billboard in chapter Highway 17.
Kill 30 enemies with thrown physics objects.
Get the Gravity Gun in Black Mesa East.
Destroy the hunter-chopper in Half-Life 2.
Get the airboat's mounted gun.
Get the airboat.
Beat all six Portal advanced maps.
Beat four Portal advanced maps.
Beat two Portal advanced maps.
Fall 30,000 feet.
Get the crowbar.
Escape the apartment block raid.
Complete Portal.
Make the correct party escort submission position decision.
Do whatever it takes to survive.
Knock down a turret with another turret.
Acquire the fully powered Aperture Science Handheld Portal Device.
