Here is the full list of all 66 Alien Swarm achievements.
Complete a campaign on Normal difficulty or harder without any marines dying.
Complete SynTek Residential within 2:30 on Normal difficulty or harder without any marines dying.
Kill 250 Swarm with a Rail Rifle.
Complete Timor Station within 4:25 on Normal difficulty or harder without any marines dying.
Kill 5,000 Swarm.
Complete Sewer Junction within 1:30 on Normal difficulty or harder without any marines dying.
Kill 100 Swarm with Incendiary Mines.
Kill 250 Swarm with a Vindicator.
Kill 250 Swarm with a Tesla Cannon.
Kill 250 Swarm with an Autogun.
Kill 100 Swarm with Laser Tripmines.
Kill 500 Swarm with deployable Sentry Guns.
Kill 250 Swarm with Twin Pistols.
Kill 250 Swarm with a Flamethrower.
Kill 100 Swarm Grubs.
Kill 6 Swarm with a single Grenade.
Kill 100 Swarm with Hornet Barrages.
Heal all 4 marines with a single Heal Beacon.
Complete the Jacob's Rest campaign on Hard difficulty or harder.
Kill 250 Swarm with PDWs.
Kill 250 Swarm with a Prototype Rifle.
Complete 10 wire hacks without access being logged.
Heal 300 points of damage in a single mission without dealing any non-melee damage to the Swarm.
Deploy 10 ammo stashes that are used by other marines.
Stun 6 Swarm with a single Stun Grenade.
Kill 5 Swarm with explosive barrels in a single mission.
Seal a door with the welder.
Destroy all Swarm Eggs in a mission without allowing any to hatch.
Cure an Infested marine.
Complete Rydberg Reactor within 3:10 on Normal difficulty or harder without any marines dying.
Freeze 6 Swarm with a single Freeze Grenade.
Kill 250 Swarm with a Shotgun.
Complete Deima Surface Bridge within 2:30 on Normal difficulty or harder without any marines dying.
Roll under a Swarm Ranger projectile.
Unlock all the available weapons.
Complete Cargo Elevator within 2:50 on Normal difficulty or harder without any marines dying.
Kill 15 Swarm with all four marines under the effects of a Damage Amp in a single mission.
Kill 1,000 Swarm.
Complete Landing Bay within 1:25 on Normal difficulty or harder without any marines dying.
Complete a mission with better than 90% accuracy.
Kill 250 Swarm with the Assault Rifle.
Complete the Jacob's Rest campaign on Easy difficulty or harder.
Complete the Jacob's Rest campaign on Normal difficulty or harder.
Complete a mission with no friendly fire incidents. Four marines must be present in the mission.
Deliver the finishing blow to a Swarm Shieldbug.
Kill a Swarm Parasite with a melee attack.
Kill 20 Swarm with melee attacks in a single mission.
Successfully perform a fast reload.
Successfully perform 5 fast reloads in a row.
Complete 2 co-op missions online. Earns a Team Fortress 2 parasite hat.
Kill 25 drones without friendly fire. Four marines must be present in the mission.
Finish a mission without the tech getting killed.
Complete a mission on Normal difficulty or harder without any marines dying.
Guard the squad's tech so that he takes no damage during the hack.
Kill a Swarm Boomer before it inflates.
Complete a mission on Normal difficulty or harder without receiving any damage.
Complete 10 computer hacks without access being logged.
Kill 250 Swarm with a Chainsaw.
Kill 250 Swarm with a Minigun.
Kill 250 Swarm with a Marksman Rifle.
Kill 250 Swarm with a Grenade Launcher.
Awarded for finishing the Jacob campaign on Insane difficulty.
Kill 25,000 Swarm.
Kill 100,000 Swarm.
Awarded for finishing the Jacob campaign on Brutal difficulty.
Complete any mission on Brutal difficulty with Onslaught and Hardcore Friendly Fire enabled.