Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement	How to unlock
Barrel Rolled ( 50 points )	Kill a Special Infected with an exploding barrel.
Chaos Generator ( 50 points )	Have all 3 generators running at once in "The Sacrifice" finale.
Kill Bill ( 50 points )	Have Bill sacrifice himself for the team.
Sacrifizzle ( 50 points )	As a Special Infected, incap someone who is trying to sacrifice themselves.
Supreme Sacrifice ( 50 points )	Complete "The Sacrifice".