Here is the full list of all 45 Aliens: Dark Descent achievements.
Complete Mission 12.
Complete Mission 11.
Kill every Queen during a campaign.
Advance a Tecker to level 10.
Remove a Trait from a marine.
Advance a Gunner to level 10.
Complete Mission 10.
Advance a Sergeant to level 10.
During a campaign, unlock every weapons.
Complete Mission 09.
Advance a Medic to level 10.
Complete Mission 08.
Complete Mission 07.
Complete Mission 06.
Have one Sentry kill at least 10 aliens.
Unlock the APC.
Save a Marine from being incubated.
Kill an enemy by using an explosive barrel.
Complete Mission 05.
Complete Mission 04.
Complete Mission 03.
Complete Mission 02.
During a campaign, kill 100 Xenomorphs.
During a campaign, secure 5 survivors.
Kill an enemy before they detect the squad.
Complete Mission 01.
Kill every Alien of a Massive Onslaught.
Save a marine from dying of Bleeding.
Secure an unconscious marine.
In any mission, complete at least one objective with only one marine in the squad.
Prevent a marine from being Abducted.
Finish the Prologue.
Finish the game on Medium.
Finish the game on Hard.
Finish the game on Nightmare.
Finish the game on "No One Can Hear Them Scream" mode.
Advance a Recon to level 10.
During a campaign, advance each Marine Class to level 10.
Lure a Queen into a Mine.
Keep all of your marines alive during a campaign.
Gather all datapads.
Destroy 4 eggs with one grenade or an RPG shot.
Make the ARC/APC run over an enemy.
During a campaign, unlock every Xeno Tech.
Have a marine with at least 2 Prostheses.