Run over 20 enemies with the car in Episode Two.
Find every radar cache in chapter Under The Radar.
Unlock the rocket launcher lambda cache in chapter Under The Radar.
Beat DOG in a race to the White Forest base.
Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.
Destroy the gunship in the hospital attic.
Escape City 17 with Alyx.
Kill an acid antlion worker.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Steal a Zombine's grenade.
Survive the rooftop strider battle in the ruins of City 17.
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.
Help Alyx snipe 30 enemies in Episode One.
Gain command of a squad of rebels in the uprising.
Kill an enemy by planting a hopper mine.
Kill an Elite Soldier with his own energy ball.
Get through the toxic tunnel under City 17 in Half-Life 2.
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.
Break the mini-teleporter in Kleiner's lab.
Kill 3 enemies using the crane.
Pin a soldier to the billboard in chapter Highway 17.
Destroy six gunships in Half-Life 2.
Use the antlions to kill 50 enemies.
Kill an enemy with a toilet.
Survive the second turret standoff in Nova Prospekt.
Kill 30 enemies with thrown physics objects.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
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.
Get the airboat.
Get the airboat's mounted gun.
Beat all six Portal advanced maps.
Escape the apartment block raid.
Get the crowbar.
Beat two Portal advanced maps.
Beat four Portal advanced maps.
Make the correct party escort submission position decision.
Complete Portal.
Acquire the fully powered Aperture Science Handheld Portal Device.
Do whatever it takes to survive.
Fall 30,000 feet.
Knock down a turret with another turret.
Defeat the chopper in Episode Two without any misses.
Send the garden gnome into space.
Save all buildings outside the missile silo from destruction.
Kill a Hunter with its own flechettes.
Jump 300 feet.
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.
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.
Use flares to light 15 zombies on fire.
Kill five barnacles with one barrel.
Use DOG's ball to make a basket in Eli's scrapyard.
Play through Ravenholm using only the Gravity Gun.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Find all lambda caches in Half-Life 2.
Use the cars to squash 15 antlions in Episode One.
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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