Here is the full list of all 12 Radiant Silvergun achievements worth 200 gamerscore.
Upload a score to the Leaderboards
Use Hyper Sword
Find hidden bonus
Destroy a boss with 100% destruction
Clear Arcade Mode
Clear Story Mode
Get three weapons to maximum level
Get 100,000 points by chain bonus
Clear Arcade Mode without using continues
Destroy all bosses 100%
Clear level 1 using only the Sword
Find all hidden bonuses