Full list of all 85 XCOM: Enemy Unknown achievements. It takes around 200 hours to unlock all of the achievements in the base game on Windows.
The base game contains 50 achievements, and there are 2 DLC packs containing 35 achievements.
Complete a Very Hard abduction mission in five turns or less on Classic or Impossible difficulty.
Beat the game in Ironman mode on Classic or Impossible Difficulty.
Beat the game on any difficulty.
Beat the game on Classic difficulty.
Have a soldier survive every mission in a full game.
Make contact with the Ethereal hive mind.
Staff the Research Labs with 80 scientists.
Staff the Engineering Department with 80 engineers.
In a single game, complete every Foundry project.
In a single game, shoot down one of each alien craft.
Build the Gollop Chamber.
Earn the "Excellent" rating in every performance category on a terror mission.
In a single game, complete every Research Project.
In a single game, complete every Autopsy.
Kill 500 aliens.
Successfully assault an Overseer UFO.
Find a soldier with the Gift.
Build the Hyperwave Relay.
Kill an alien while flying. Single player only.
Build a suit of powered armor.
Acquire 1000 credits in one month.
Build a Firestorm.
Get satellite coverage over every country on one continent.
Build a S.H.I.V.
Build a Laboratory.
Recover the Hyperwave Beacon.
Uncover the alien base's location.
Advance one of your soldiers to Colonel rank.
Stun an Outsider.
Capture a live alien.
Gain access to the lowest level in your base.
Build a Workshop.
Launch a Satellite.
Fulfill a Council request.
Build a base facility.
Clear a UFO crash site with one soldier on Classic or Impossible difficulty.
Win a mission with an all-female squad. Single player only.
Shoot down a UFO.
Build an item.
Complete a Research Project.
Complete a mission without losing a soldier.
Complete the tutorial mission.
Kill 50 aliens with explosive weapons.
Kill 150 aliens.
Win a multiplayer match.
Mind Control an Ethereal. Single player only.
Beat the game on Impossible difficulty.
Shoot down 40 UFOs.
Play a multiplayer match against someone with this achievement.
Win the game from each of the 5 starting locations.
Take your new ally into the final challenge.
Complete Gangplank.
Complete Confounding Light.
Complete Friends in Low Places.
Complete Confounding Light with more than 3 turns left on the timer.
Field a squad with 4 augmented soldiers, each with a different base ability and win the mission
Field a squad consisting entirely of augmented soldiers and SHIVs (min. 4) and win the mission
Deal with the newest global threat
Make certain of the new threat's location
Field a squad where all members have at least two modifications (min. 4) and win the mission
Kill an enemy as it is psionically attacking you in single player
Kill a Muton Berserker in melee combat in single player
Kill an unseen enemy detected by a specially modified soldier in single player
Eradicate the infestation
Use Collateral Damage to blow up a car in single player
Have your special-duty soldier kill three enemies in the same mission
Jump two stories in one move in single player
Get a Soldier to have 5 modifications in single player
Proc Combat Rush on the entire squad (min. 4)
Deploy three tactical subsystems on a single soldier in single player
Complete Furies
Kill an elite enemy Medic with explosive damage in single player
Kill an elite enemy Sniper with one of your own snipers in single player
Field a fully enhanced squad and win the mission
Complete Deluge
Eliminate all alien waves
Eliminate an enemy's shield and kill it on the same turn in single player
Get at least 4 kills with XCOM Base Security personnel
Modify a soldier in single player
Beat a new special mission without losing any assets
Cause an enemy to suicide
Augment a soldier in single player
Stop a squad member from suffocating in single player
Beat the game without buying a Squad Size upgrade (Classic+ difficulty)
Designate a highly decorated soldier as the Volunteer