Complete each achievement to get the allotted gamerscore. The numbers between the () are the amount of points your recieve for each achievement.
11th Clan of the S'pht (27) - Venture into the Citadel and learn the secrets of the S'pht.
Bigger Guns Nearby (14) - Find the Assault Rifle in a Single player or Co-Op Game.
Bob-B-Q (14) - They're Everywhere!
Hats off to 819 (21) - The secret of 2401 lies within.
I'm Invincible! (10) - Kill an invincible opponent with the Fusion Pistol in a Multiplayer game.
Make Someone Pay (10) - Get 20 Rocket Launcher kills in a Multiplayer game.
Pfhor Score and Seven Years Ago (10) - Win a Multiplayer game.
Pfhor the Win (42) - Complete the Single player game in any difficulty.
SEVEN (7) - Get seven fist kills in the game.
Tastes Like Chicken (10) - Get 20 Tozt-7 kills in a Multiplayer game.