Here is the full list of all 23 Gamma Blast achievements.
Destroy most enemies on stage 1
Destroy most enemies on stage 2
Destroy most enemies on stage 3
Destroy most enemies on stage 4
Destroy most enemies on stage 5
Destroy most enemies on stage 6
Destroy most enemies on stage 7
Destroy Enforcer
Destroy Reaper
Destroy COD
Destroy Deadlock
Destroy Grinder
Destroy Warp-Worm
Destroy Destroyer
Complete the game
Complete stage 1 without losing a single life
Complete stage 2 without losing a single life
Complete stage 3 without losing a single life
Complete stage 4 without losing a single life
Complete stage 5 without losing a single life
Complete stage 6 without losing a single life
Complete stage 7 without losing a single life
Complete the game without losing a single life