Complete the following achievements to unlock Xbox Live Gamerscore points:

The Terror Begins (50 points): Escape from the graveyard of terror.
A Changed Father (50 points): Liberate the changed man.
Beyond the Shades (50 points): Encounter a former S.T.A.R.S. captain.
The Fallen Tyrant (100 points): Flatten an unstoppable enemy.
The Prisoner Who Lost Everything (100 points): Defeat the nameless man and end his suffering.
To The Frozen Land (50 points): Begin the search for your sister.
The Arrogant Queen (150 points): Put an end to the Queen's reign.
Duty and Humanity (50 points): Deliver some medicine to a man in need.
Weapon Crazy (150 points): Get the Rocket Launcher.
Battle Master (150 points): Get the Linear Launcher from Battle Game.
From The Young Lady (50 points): Receive encouragement from a young lady.
The Green Giant (50 points): Say farewell to your fallen comrade.