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