• 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.

• Landfall (20) - first mission
  
• Holdout (20) - second mission
• The Road (20) - third mission
  
• Assault (30) - fourth mission
• Cleansing (30) - fifth mission
  
• Refuge (30) - sixth mission
• Last Stand (40) - seventh mission
• The Key (40) - eighth mission
  
• Return (50) - final mission

• Guerilla (10) - first mission
  
• Demon (10) - second mission
  
• Cavalier (10) - third mission
• Askar (10) - fourth mission
  
• Exterminator (10) - fifth mission
• Ranger (10) - sixth mission
  
• Vanguard (10) - seventh mission
  
• Orpheus (10) - eighth mission
• Reclaimer (10) - final mission

• Black Eye (10)
  
• Catch (10)
• Famine (10)
  
• Fog (10)
• Iron (10)
• Mythic (10)
• Thunderstorm (10)
• Tilt (10)

• Killing Frenzy (5) - Kill 10 enemies without dying in any ranked free for all playlist.
• Lee R Wilson Memorial (5) - Score 5 grenade sticks in any ranked free for all playlist.
• Mongoose Mowdown (5) - Splatter an enemy with the mongoose in a ranked free for all playlist.
• Maybe Next Time Buddy (5) - Board the same vehicle within 10 seconds after being boarded in any free for all playlist.
• MVP (5) - Earn the MVP in any ranked playlist.
• Overkill (5) - Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist.
• Steppin' Razor (5) - Score a Triple Kill with the sword in a ranked free for all playlist.
• Triple Kill (5) - Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist.
• Two for One (5) - Score a Double Kill with a single spartan laser shot in a ranked free for all playlist.
• Up Close and Personal (5) - Kill 5 enemies by melee or assassination in a ranked free for all playlist.
  
• Graduate (10) - Earn 5 EXP or finish 10 games to complete the requirements for basic training.
• UNSC Spartan (15) - Earn your Sergeant rating to be recognized as a true Spartan.
• Spartan Officer (25) - Advance to the Spartan Officer ranks.

• Fear the Pink Mist (5) - Kill 5 enemies with the needler in a ranked free for all playlist or in campaign.
• Headshot Honcho (5) - Kill 10 enemies with headshots in a ranked free for all playlist or in campaign.
• Too Close to the Sun (5) - Destroy an enemy banshee with the spartan laser or missile pod in a ranked playlist or in campaign.
• Used Car Salesman (5) - Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign.
• We're in for Some Chop (5) - Destroy an enemy vehicle with equipment in a ranked playlist or in campaign.
• Tough Luck (10) - Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
• Marathon Man (40) - Locate and access all Terminals in the Campaign.

Via GamePro