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