Get five kills in a row without dying.
Contain the Citadel core without killing any stalkers.
Destroy six gunships in Half-Life 2.
Continue playing to unlock this secret achievement.
Win 20 games.
Get five revenge kills.
Successfully defend Gravel Pit without giving up a capture.
Win Hydro without giving up a capture.
Play a complete game on every map.
Successfully defend Dustbowl without giving up a capture.
Win Well in 5 minutes or less.
Detach security cameras from the walls.
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.
Help Alyx snipe 30 enemies in Episode One.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Pin a soldier to the billboard in chapter Highway 17.
Play through Ravenholm using only the Gravity Gun.
Win 2Fort with a shutout.
Save all buildings outside the missile silo from destruction.
Kill five enemies with a Manhack.
Kill five barnacles with one barrel.
Use DOG's ball to make a basket in Eli's scrapyard.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Break the mini-teleporter in Kleiner's lab.
Send the garden gnome into space.
Kill a Hunter with its own flechettes.
Defeat the chopper in Episode Two without any misses.
Find and break every web cache in Episode Two.
Steal a Zombine's grenade.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Kill a Combine soldier with his own grenade.
Beat all six Portal advanced maps.
Beat four Portal advanced maps.
Beat DOG in a race to the White Forest base.
Find every radar cache in chapter Under The Radar.
Run over 20 enemies with the car in Episode Two.
Unlock the rocket launcher lambda cache in chapter Under The Radar.
Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.
Kill an enemy by planting a hopper mine.
Kill an acid antlion worker.
Escape City 17 with Alyx.
Destroy the gunship in the hospital attic.
Survive long enough to get on the parking garage elevator.
Use the cars to squash 15 antlions in Episode One.
Contain the Citadel core.
Kill an Elite Soldier with his own energy ball.
Make it to the bottom of the Citadel's main elevator shaft in one piece.
Get through the toxic tunnel under City 17 in Half-Life 2.
Gain command of a squad of rebels in the uprising.
Acquire the fully powered Aperture Science Handheld Portal Device.
Do whatever it takes to survive.
Make the correct party escort submission position decision.
Complete Portal.
Fall 30,000 feet.
Jump 300 feet.
Beat two Portal advanced maps.
Earn bronze medals on all Portal challenges.
Earn silver medals on all Portal challenges.
Earn gold medals on all Portal challenges.
Accumulate 10 turret kills with a single turret.
Trick an opposing medic into healing you.
Play in a game with seven or more players from your friends list.
Accumulate 1000 total kills.
Play a complete round with every class.
Accumulate 25000 heal points as a Medic.
Set five enemies on fire in 30 seconds.
Get 25 headshots as a Sniper.
Knock down a turret with another turret.
Kill 30 enemies with thrown physics objects.
Kill five enemies with the same energy ball.
Use flares to light 15 zombies on fire.
Escape the apartment block raid.
Get the crowbar.
Get the airboat.
Get the airboat's mounted gun.
Destroy the hunter-chopper in Half-Life 2.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Get the Gravity Gun in Black Mesa East.
Kill 3 enemies using the crane.
Use the antlions to kill 50 enemies.
Kill an enemy with a toilet.
Survive the second turret standoff in Nova Prospekt.
Survive the generator plaza standoff in chapter Anticitizen One.
Kill all of the snipers in City 17.
Shut down the supression device by disabling its generators.
Survive the rooftop strider battle in the ruins of City 17.
Find all lambda caches in Half-Life 2.
Squish every antlion grub in Episode Two.
