Achievements:
Askar (10)
Score over 15,000 points in the Campaign meta-game on the fourth mission.

Assault (30)
Finish the fourth mission of the Campaign on Normal, Heroic, or Legendary.

Black Eye (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Campaign Complete: Heroic (125)
Finish the Campaign on Heroic (normal is unlocked as well).

Campaign Complete: Legendary (125)
Finish the Campaign on Legendary (normal and heroic are unlocked as well).

Campaign Complete: Normal (125)
Finish the Campaign on Normal.

Catch (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Cavalier (10)
Score over 15,000 points in the Campaign meta-game on the third mission.

Cleansing (30)
Finish the fifth mission of the Campaign on Normal, Heroic, or Legendary.

Demon (10)
Score over 15,000 points in the Campaign meta-game on the second mission.

Exterminator (10)
Score over 15,000 points in the Campaign meta-game on the fifth mission.

Famine (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Fear the Pink Mist (5)
Kill 5 enemies with the needler in a ranked free for all playlist or in campaign.

Fog (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Graduate (10)
Earn 5 EXP or finish 10 games to complete the requirements for basic training (Online).

Guerilla (10)
Score over 15,000 points in the Campaign meta-game on the first mission.

Headshot Honcho (5)
Kill 10 enemies with headshots in a ranked free for all playlist or in campaign.

Holdout (20)
Finish the second mission of the Campaign on Normal, Heroic, or Legendary.

Iron (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Killing Frenzy (5)
Kill 10 enemies without dying in any ranked free for all playlist (Online).

Landfall (20)
Finish the first mission of the Campaign on Normal, Heroic, or Legendary.

Last Stand (40)
Finish the seventh mission of the Campaign on Normal, Heroic, or Legendary.

Lee R Wilson Memorial (5)
Score 5 grenade sticks in any ranked free for all playlist (Online).

Marathon Man (40)
Locate and access all Terminals in the Campaign.

Maybe Next Time Buddy (5)
Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online).

Mongoose Mowdown (5)
Splatter an enemy with the mongoose in a ranked free for all playlist (Online).

MVP (5)
Earn the MVP in any ranked playlist (Online).

Mythic (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Orpheus (10)
Score over 15,000 points in the Campaign meta-game on the eigth mission.

Overkill (5)
Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (Online).

Ranger (10)
Score over 50,000 points in the Campaign meta-game on the sixth mission.

Reclaimer (10)
Score over 15,000 points in the Campaign meta-game on the final mission.

Refuge (30)
Finish the sixth mission of the Campaign on Normal, Heroic, or Legendary.

Return (50)
Finish the final mission of the Campaign on Normal, Heroic, or Legendary.

Spartan Officer (25)
Advance to the Spartan Officer ranks (Online).

Steppin' Razor (5)
Score a Triple Kill with the sword in a ranked free for all playlist (Online).

The Key (40)
Finish the eigth mission of the Campaign on Normal, Heroic, or Legendary.

The Road (20)
Finish the third mission of the Campaign on Normal, Heroic, or Legendary.

Thunderstorm (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Tilt (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Too Close to the Sun (5)
Destroy an enemy banshee with the spartan laser or missile pod in a ranked playlist or in campaign.

Tough Luck (10)
Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.

Triple Kill (5)
Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist (Online).

Two for One (5)
Score a Double Kill with a single spartan laser shot in a ranked free for all playlist (Online).

UNSC Spartan (15)
Earn your Sergeant rating to be recognized as a true Spartan (Online).

Up Close and Personal (5)
Kill 5 enemies by melee or assassination in a ranked free for all playlist (Online).

Used Car Salesman (5)
Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign.

Vanguard (10)
Score over 50,000 points in the Campaign meta-game on the seventh mission.

We’re in for Some Chop (5)
Destroy an enemy vehicle with equipment in a ranked playlist or in campaign.


Armor Permutations:
Elite:
Ascetic Body: Unlock "Up Close and Personal" Achievement 
Ascetic Head: Unlock "Steppin' Razor" Achievement 
Ascetic Shoulders: Unlock "Overkill" Achievement 
Commando Body: Unlock "Triple Kill" Achievement 
Commando Head: Unlock "Overkill" Achievement 
Flight Body: Complete Tsavo Highway On Herioic or Legendary 
Flight Head: Complete Campaign mode on Heroic difficulty. 
Flight Shoulders: Complete The Ark on Heroic difficulty or higher. 
Spartan:
EOD Body: Complete Tsavo Highway on Legendary 
EOD Head: Complete Campaign mode on Legendary Difficulty 
EOD Shoulders: Complete The Ark on Legendary difficulty 
EVA Body: Complete Tsavo Highway on Normal or higher 
EVA Head: Complete Campaign mode on Normal 
EVA Shoulders: Complete The Ark on Normal difficulty or higher. 
Hayabusa Chest: Collect 5 hidden skulls 
Hayabusa Helmet: Collect 13 hidden skulls 
Hayabusa Shoulders: Collect 9 hidden skulls 
Katana: Complete all Achievements (1000/1000) 
Mark V Head: Unlock "UNSC Spartan" Achievement 
ODST Head: Unlock "Spartan Graduate" Achievement 
Rogue Head: Unlock "Spartan Officer" Achievement 
Scout Body: Unlock "Too Close to the Sun" Achievement 
Scout Head: Unlock "Used Car Salesman" Achievement 
Scout Shoulders: Unlock "Mongoose Mowdown" Achievement 
Security Head: Earn 1000 Gamerscore points.