Achievments in halo
Thanks to Gamewinner.com
Landfall (20 points): Finish the first mission of the Campaign on Normal, Heroic, or Legendary.
Holdout (20 points): Finish the second mission of the Campaign on Normal, Heroic, or Legendary.
The Road (20 points): Finish the third mission of the Campaign on Normal, Heroic, or Legendary.
Assault (30 points): Finish the fourth mission of the Campaign on Normal, Heroic, or Legendary.
Cleansing (30 points): Finish the fifth mission of the Campaign on Normal, Heroic, or Legendary.
Refuge (30 points): Finish the sixth mission of the Campaign on Normal, Heroic, or Legendary.
Last Stand (40 points): Finish the seventh mission of the Campaign on Normal, Heroic, or Legendary.
The Key (40 points): Finish the eighth mission of the Campaign on Normal, Heroic, or Legendary.
Return (50 points): Finish the final mission of the Campaign on Normal, Heroic, or Legendary.
Campaign Complete: Normal (125 points): Finish the Campaign on Normal.
Campaign Complete: Heroic (125 points): Finish the Campaign on Heroic (unlocks achievement for Normal, if not earned).
Campaign Complete: Legendary (125 points): Finish the Campaign on Legendary (unlocks achievements for Normal and Heroic, if not earned).
Iron (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Black Eye (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Tough Luck (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Catch (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Fog (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Famine (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Thunderstorm (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Tilt (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Mythic (10 points): Find and claim this skull when playing on Normal, Heroic or Legendary difficulty.
Graduate (10 points): Earn 5 EXP or finish 10 games to complete the requirements for basic training (Online).
UNSC Spartan (15 points): Earn your Sergeant rating to be recognized as a true Spartan (Online).
Spartan Officer (25 points): Advance to the Spartan Officer ranks (Online).
Two for One (5 points): Score a Double Kill with a single Spartan laser shot in a ranked free for all playlist (Online).
Too Close to the Sun (5 points): Destroy an enemy Banshee with the Spartan laser or missile pod in a ranked playlist or in campaign.
Triple Kill (5 points): Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist (Online).
Overkill (5 points): Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (Online).
Lee R Wilson Memorial (5 points): Score 5 grenade sticks in any ranked free for all playlist (Online).
We're in for some Chop (5 points): Destroy an enemy vehicle with equipment in a ranked playlist or in campaign.
Killing Frenzy (5 points): Kill 10 enemies without dying in any ranked free for all playlist (Online).
Steppin' Razor (5 points): Score a Triple Kill with the sword in a ranked free for all playlist (Online).
Mongoose Mowdown (5 points): Splatter an enemy with the mongoose in a ranked free for all playlist (Online).
Up Close and Personal (5 points): Kill 5 enemies by melee or assassination in a ranked free for all playlist (Online).
Fear the Pink Mist (5 points): Kill 5 enemies with the needler in a ranked free for all playlist or in campaign.
Headshot Honcho (5 points): Kill 10 enemies with headshots in a ranked free for all playlist or in campaign.
Used Car Salesman (5 points): Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign.
Marathon Man (40 points): Locate and access all Terminals in the Campaign.
MVP (5 points): Earn the MVP in any ranked playlist (Online).
Maybe Next Time Buddy (5 points): Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online).
Guerilla (10 points): Score over 15,000 points in the Campaign meta-game on the first mission.
Demon (10 points): Score over 15,000 points in the Campaign meta-game on the second mission.
Cavalier (10 points): Score over 15,000 points in the Campaign meta-game on the third mission.
Askar (10 points): Score over 15,000 points in the Campaign meta-game on the fourth mission.
Exterminator (10 points): Score over 15,000 points in the Campaign meta-game on the fifth mission.
Ranger (10 points): Score over 50,000 points in the Campaign meta-game on the sixth mission.
Vanguard (10 points): Score over 50,000 points in the Campaign meta-game on the seventh mission.
Orpheus (10 points): Score over 15,000 points in the Campaign meta-game on the eighth mission.
Reclaimer (10 points): Score over 15,000 points in the Campaign meta-game on the final mission.
I got this imformation from Gamewinners.com
hope this helps a few people in their quest to get all achievments