The aliens are trying to take over in XCOM: Enemy Unkown, so how about some achievements, and some secret ones as well.
There are fifteen secret achievements to unlock in the game, listed at the bottom.
…and Practice (10) – Build a Workshop
A Continental Fellow (50) – Win the game from each of the 5 starting locations
Ain’t No Cavalry Comin’ (50) – Have a soldier survive every mission in a full game
All Employees Must Wash Hands… (10) – In a single game, complete every Autopsy
All Together Now (10) – Get satellite coverage over every country on one continent
And So It Begins… (15) – Complete the tutorial mission
As A Scalpel (25) – Earn the “Excellent” rating in every performance category on a terror mission
Bada Boom (10) – Kill 50 aliens with explosive weapons
Combat Ready (5) – Build an item
Drums in the Deep (10) – Gain access to the lowest level in your base
Earth First (60) – Beat the game on Classic difficulty
Edison (25) – In a single game, complete every Research Project
Eye in the Sky (5) – Launch a Satellite
Happy to Oblige (15) – Fulfill a Council request
Humanity’s Savior (30) – Beat the game on any difficulty
Hunter/Killer (15) – In a single game, shoot down one of each alien craft
Lone Wolf (20) – Clear a UFO crash site with one soldier on Classic or Impossible difficulty
Man No More (10) – Build a suit of powered armor
No Looking Back (100) – Beat the game in Ironman mode on Classic or Impossible difficulty
One Gun at a Time (20) – Staff the Engineering Department with 80 engineers
Oppenheimer (20) – Staff the Research Labs with 80 scientists
Our Finest Hour (90) – Beat the game on Impossible difficulty
Pale Horse (50) – Kill 500 aliens
Shooting Stars (35) – Shoot down 40 UFOs
Skunkworks (20) – In a single game, complete every Foundry project
Tables Turned (10) – Shoot down a UFO
The Hardest Road (10) – Advance one of your soldiers to Colonel rank
Theory… (10) – Build a Laboratory
Up and Running (5) – Build a base facility
We Happy Few (10) – Complete a mission without losing a soldier
Welcoming Committee (20) – Kill 150 aliens
Wet Work (10) – Complete a Very Hard abduction mission in five turns or less on Classic or Impossible difficulty
What Wonders Await (5) – Complete a Research Project
Worth Every Penny (20) – Acquire 1000 credits in one month
You Have 5 Seconds to Comply (10) – Build a S.H.I.V.
Here are the fifteen secret achievements to unlock in the game.
And Hell’s Coming With Me (10) – Successfully assault an Overseer UFO
Angel of Death (10) – Kill an alien while flying (Single player only)
Beyond the Veil (10) – Find a soldier with the Gift
Flight of the Valkyries (10) – Win a mission with an all-female squad (Single player only)
Meet New People. Then Kill Them. (10) – Win a multiplayer match
Off My Planet (25) – Recover the Hyperwave Beacon
On the Shoulders of Giants (10) – Build the Gollop Chamber
Poison Control (10) – Cure poison on five soldiers in a single mission (Single player only)
Prisoner of War (10) – Capture a live alien
Ride the Lightning (10) – Build a Firestorm
See All, Know All (10) – Build the Hyperwave Relay
The Gatekeeper (10) – Stun an Outsider
The Volunteer (10) – Make contact with the Ethereal hive mind
X Marks the Spot (10) – Uncover the alien base’s location
Xavier (25) – Mind Control an Ethereal. Single player only