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

Complete The Game (25 points): Play through the final scene of Gunstar Heroes.
Golden Silver (25 points): Defeat superboss Golden Silver.
O Brother (25 points): Defeat Green.
Greedy Fly (25 points): Defeat Black Fly.
Locked and Loaded (15 points): Begin the game with each weapon.
Colonel Red (15 points): Rescue Yellow by defeating Smash Daisaku.
OMG 11 Bosses (15 points): Complete the Dice Palace and defeat Black Beat Stepper.
Not Quite Red (15 points): Defeat Orange on the Flying Battleship.
Crab Attack (10 points): Defeat Crab Force in the Underground Mine.
Pink (10 points): Defeat Pinky Roader in the Ancient Ruins.
Bravoo Man (10 points): Defeat Bravoo Man in the Ancient Ruins.
Papaya Dance (10 points): Defeat Papaya Dance in the Ancient Ruins.