Accomplish the indicated achievement to get the corresponding number of Microsoft Gamerscore points:

Cairo Station (30 points): Complete Cairo Station at Normal, Heroic, or Legendary.
Outskirts (30 points): Complete Outskirts at Normal, Heroic, or Legendary.
Metropolis (30 points): Complete Metropolis at Normal, Heroic, or Legendary.
The Arbiter (30 points): Complete The Arbiter at Normal, Heroic, or Legendary.
Oracle (30 points): Complete The Oracle at Normal, Heroic, or Legendary.
Delta Halo (30 points): Complete Delta Halo at Normal, Heroic, or Legendary.
Regret (30 points): Complete Regret at Normal, Heroic, or Legendary.
Sacred Icon (30 points): Complete Sacred Icon at Normal, Heroic, or Legendary.
Quarantine Zone (30 points): Complete Quarantine Zone at Normal, Heroic, or Legendary.
Gravemind (30 points): Complete Gravemind at Normal, Heroic, or Legendary.
Uprising (30 points): Complete Uprising at Normal, Heroic, or Legendary.
High Charity (30 points): Complete High Charity at Normal, Heroic, or Legendary.
The Great Journey (30 points): Complete The Great Journey at Normal, Heroic, or Legendary.
Warrior (100 points): Complete the game on Normal difficulty.
Hero (50 points): Complete the game on Heroic difficulty.
Legend (50 points): Complete the game on Legendary difficulty.
King of the Scarab (20 points): Acquire the Scarab gun on the Metropolis level, any difficulty.
Silent but Deadly (20 points): Kill 7 opponents from behind in a row without being spotted, any level, any difficulty.
Demon (25 points): Complete any campaign level without dying once on Normal, Heroic, or Legendary.
Go Ape Shiv (20 points): Kill an enraged, berserk Brute by melee, any level, any difficulty.
Stick It (5 points): Stick an opponent with a plasma grenade and blow them up.
Counterpoint (5 points): Kill the sword carrier.
Carjacking (5 points): Steal an occupied vehicle from an opponent and take it over.
Violent Cartographer (25 points): Play every available default map and stay in each game until it's over.
Rainman (25 points): Play every available game variant, with at least 3 other players, to the end of each game.
Double Kill (20 points): Kill 2 opponents within 4 seconds.
Triple Kill (20 points): Kill 3 opponents within 4 seconds.
Killtacular (20 points): Kill 4 opponents within 4 seconds.
Killing Spree (20 points): Kill 5 opponents in a row in the same game, without dying.
Running Riot (20 points): Kill 10 opponents in a row in the same game, without dying.
Sniper Kill (10 points): Kill an opponent with the sniper rifle or the beam rifle.
Roadkill (10 points): Run over, hit and kill an opponent with a vehicle.
Bonecracker (10 points): Hit and kill an opponent with a melee attack.
Assassin (10 points): Melee an opponent from behind.
Skewer Stopper (20 points): Kill the sword carrier after they kill 5 or more times in a row with the sword.
Vigilante (10 points): Stop a Killing Spree of another player.
Air Traffic Control (20 points): Blow up the Banshee in flight while manned, with grenades or the rocket launcher.
Decorated Soldier (10 points): Get awarded at least 8 different medals in one non-team game.
Ninja (20 points): In a non-team game, kill 5 people by melee, from behind.
Flaming Ninja (20 points): Kill an opponent that has the Ninja achievement.
Hired Gun (20 points): Kill an opponent who has the Legend achievement.