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