Kill 20 Combine Soldiers/Civil Protection overall.
Kill 50 Combine Soldiers/Civil Protection overall.
Kill 100 Combine Soldiers/Civil Protection overall.
Kill 20 Hunters overall.
Kill 50 Hunters overall.
Kill 100 Hunters overall.
Reach the maximum level in a game.
Kill 100 enemies in a game.
Kill 1,000 enemies overall.
Kill 1,000,000 enemies overall.
Kill a Combine Soldier/Civil Protection with a Hunter's Flechette in a game.
Kill 10 Hunters overall with their own flechettes.
Kill 100 enemies in a game on NIGHTMARE difficulty.
Kill 20 Antlions/Antlion Workers overall.
Kill 50 Antlions/Antlion Workers overall.
Kill 100 Antlions/Antlion Workers overall.
Kill 20 Antlion Guards/Antlion Guardians overall.
Kill 50 Antlion Guards/Antlion Guardians overall.
Kill 100 Antlion Guards/Antlion Guardians overall.
Kill 20 Zombies/Fast Zombies/Poison Zombies/Zombines overall.
Kill 50 Zombies/Fast Zombies/Poison Zombies/Zombines overall.
Kill 100 Zombies/Fast Zombies/Poison Zombies/Zombines overall.
Kill 20 Headcrabs/Fast Headcrabs/Poison Headcrabs overall.
Kill 50 Headcrabs/Fast Headcrabs/Poison Headcrabs overall.
Kill 100 Headcrabs/Fast Headcrabs/Poison Headcrabs overall.
Kill 20 Houndeyes/Bullsquids/Vortigaunts overall.
Kill 50 Houndeyes/Bullsquids/Vortigaunts overall.
Kill 100 Houndeyes/Bullsquids/Vortigaunts overall.
Kill 10 enemies in a game with the SMG's Grenades.
Kill 10 enemies without firing a single bullet after starting a game.
Kill 20 enemies without getting damaged after spawning.
Kill 10 enemies while at low health.
Kill over 100 enemies before your painful demise.
Kill 10 enemies with their own grenades.