XCOM: Enemy Unknown

1. 
   No Looking Back

   Beat the game in Ironman mode on Classic or Impossible Difficulty.
   2.2%
2. 
   Meet New People. Then Kill Them.

   Win a multiplayer match.
   8.4%
3. 
   Xavier

   Mind Control an Ethereal. Single player only.
   6.1%
4. 
   Humanity's Savior

   Beat the game on any difficulty.
   32%
5. 
   Earth First

   Beat the game on Classic difficulty.
   5.8%
6. 
   Our Finest Hour

   Beat the game on Impossible difficulty.
   1.7%
7. 
   Lone Wolf

   Clear a UFO crash site with one soldier on Classic or Impossible difficulty.
   2.0%
8. 
   Bada Boom

   Kill 50 aliens with explosive weapons.
   39%
9. 
   Welcoming Committee

   Kill 150 aliens.
   63%
10. 
    Pale Horse

    Kill 500 aliens.
    41%
11. 
    Shooting Stars

    Shoot down 40 UFOs.
    8.6%
12. 
    Ain't No Cavalry Comin'

    Have a soldier survive every mission in a full game.
    2.3%
13. 
    As A Scalpel

    Earn the "Excellent" rating in every performance category on a terror mission.
    51%
14. 
    Edison

    In a single game, complete every Research Project.
    8.5%
15. 
    Angel of Death

    Kill an alien while flying. Single player only.
    23%
16. 
    All Employees Must Wash Hands…

    In a single game, complete every Autopsy.
    40%
17. 
    Beyond the VeilSecret

    Steam withholds the description of a secret achievement.
    43%
18. 
    Prisoner of WarSecret

    Steam withholds the description of a secret achievement.
    70%
19. 
    The GatekeeperSecret

    Steam withholds the description of a secret achievement.
    63%
20. 
    X Marks the SpotSecret

    Steam withholds the description of a secret achievement.
    61%
21. 
    See All, Know AllSecret

    Steam withholds the description of a secret achievement.
    45%
22. 
    On the Shoulders of GiantsSecret

    Steam withholds the description of a secret achievement.
    38%
23. 
    Ride the LightningSecret

    Steam withholds the description of a secret achievement.
    47%
24. 
    Eye in the Sky

    Launch a Satellite.
    82%
25. 
    All Together Now

    Get satellite coverage over every country on one continent.
    51%
26. 
    Hunter/Killer

    In a single game, shoot down one of each alien craft.
    18%
27. 
    Man No More

    Build a suit of powered armor.
    49%
28. 
    Bubonic

    Play a multiplayer match against someone with this achievement.
    6.1%
29. 
    We Happy Few

    Complete a mission without losing a soldier.
    87%
30. 
    The Hardest Road

    Advance one of your soldiers to Colonel rank.
    57%
31. 
    Worth Every Penny

    Acquire 1000 credits in one month.
    48%
32. 
    Oppenheimer

    Staff the Research Labs with 80 scientists.
    30%
33. 
    One Gun at a Time

    Staff the Engineering Department with 80 engineers.
    33%
34. 
    Skunkworks

    In a single game, complete every Foundry project.
    14%
35. 
    You Have 5 Seconds to Comply

    Build a S.H.I.V.
    39%
36. 
    Theory...

    Build a Laboratory.
    58%
37. 
    ...and Practice.

    Build a Workshop.
    63%
38. 
    Wet Work

    Complete a Very Hard abduction mission in five turns or less on Classic or Impossible difficulty.
    6.2%
39. 
    A Continental Fellow

    Win the game from each of the 5 starting locations.
    1.0%
40. 
    What Wonders Await

    Complete a Research Project.
    86%
41. 
    Up and Running

    Build a base facility.
    79%
42. 
    Combat Ready

    Build an item.
    86%
43. 
    Drums in the Deep

    Gain access to the lowest level in your base.
    46%
44. 
    Happy to Oblige

    Fulfill a Council request.
    71%
45. 
    And Hell's Coming With MeSecret

    Steam withholds the description of a secret achievement.
    40%
46. 
    Off My PlanetSecret

    Steam withholds the description of a secret achievement.
    52%
47. 
    Tables Turned

    Shoot down a UFO.
    81%
48. 
    And So It Begins…

    Complete the tutorial mission.
    83%
49. 
    The VolunteerSecret

    Steam withholds the description of a secret achievement.
    35%
50. 
    Flight of the Valkyries

    Win a mission with an all-female squad. Single player only.
    28%
51. 
    New FriendSecret

    Steam withholds the description of a secret achievement.
    36%
52. 
    Bait the HookSecret

    Steam withholds the description of a secret achievement.
    31%
53. 
    The Bigger They AreSecret

    Steam withholds the description of a secret achievement.
    29%
54. 
    Rising DragonSecret

    Steam withholds the description of a secret achievement.
    9.1%
55. 
    All AboardSecret

    Steam withholds the description of a secret achievement.
    11%
56. 
    Who Needs Limbs?

    Augment a soldier in single player
    30%
57. 
    A Little Bit Alien

    Modify a soldier in single player
    30%
58. 
    Enemy Within

    Get a Soldier to have 5 modifications in single player
    14%
59. 
    Steel Martyr

    Deploy three tactical subsystems on a single soldier in single player
    19%
60. 
    Apotheosis Denied

    Deal with the newest global threat
    20%
61. 
    They Shall Not Pass

    Eliminate all alien waves
    23%
62. 
    Zom-B-Gone

    Eradicate the infestation
    27%
63. 
    An Army Of Four

    Beat the game without buying a Squad Size upgrade (Classic+ difficulty)
    1.2%
64. 
    The Meld Squad

    Field a fully enhanced squad and win the mission
    12%
65. 
    Shieldbuster

    Eliminate an enemy's shield and kill it on the same turn in single player
    26%
66. 
    Someone Your Own Size

    Kill a Muton Berserker in melee combat in single player
    12%
67. 
    Taking A Load Off

    Stop a squad member from suffocating in single player
    37%
68. 
    Where in the World

    Make certain of the new threat's location
    16%
69. 
    Mind the Step

    Jump two stories in one move in single player
    16%
70. 
    Nice Cover

    Use Collateral Damage to blow up a car in single player
    13%
71. 
    By Our Powers Combined

    Field a squad with 4 augmented soldiers, each with a different base ability and win the mission
    2.4%
72. 
    Rise of the Machines

    Field a squad consisting entirely of augmented soldiers and SHIVs (min. 4) and win the mission
    3.5%
73. 
    Mutatis Mutandis

    Field a squad where all members have at least two modifications (min. 4) and win the mission
    4.7%
74. 
    Mental Minefield

    Kill an enemy as it is psionically attacking you in single player
    5.1%
75. 
    Anger Management

    Proc Combat Rush on the entire squad (min. 4)
    12%
76. 
    Remington… Max Remington

    Have your special-duty soldier kill three enemies in the same mission
    13%
77. 
    G’day

    Kill an elite enemy Sniper with one of your own snipers in single player
    24%
78. 
    Regenerate This

    Kill an elite enemy Medic with explosive damage in single player
    20%
79. 
    Tingling Sensation

    Kill an unseen enemy detected by a specially modified soldier in single player
    5.8%
80. 
    Pain in the Neck

    Cause an enemy to suicide
    17%
81. 
    Solid Prospect

    Complete Deluge
    21%
82. 
    Ours are the Furies

    Complete Furies
    19%
83. 
    Elite Defense

    Beat a new special mission without losing any assets
    28%
84. 
    Guardian of Earth

    Designate a highly decorated soldier as the Volunteer
    2.7%
85. 
    All Hands on Deck

    Get at least 4 kills with XCOM Base Security personnel
    22%

Names, descriptions and icons are the game’s own, as Steam publishes them; the share is how many owners have unlocked each, from Steam's global figures for 85 of them.