Here is the full list of all 12 Geometry Wars: Retro Evolved achievements worth 200 gamerscore.
Earn 1,000,000 points without dying
Earn x10 multiplier
Earn 500,000 points without dying
Collect 9 lives
Collect 9 bombs
Earn 1,000,000 points
Earn 500,000 points
Earn 250,000 points without dying
Earn 100,000 points without dying
Earn 250,000 points
Earn 100,000 points
Survive the first 60 seconds of the game without firing