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