Here is the full list of all 37 Batsugun achievements.
Complete Stage 3 in the Special version
Complete Stage 2 in the Special version
Complete Stage 1 in the Special version
First death of many achieved
Play a hundred games
Accumulate a thousand deaths
Pick up 100 bombs
Complete Stage 1 in the Normal version
Complete Stage 2 in the Normal version
Complete Stage 3 in the Normal version
Complete Stage 4 in the Normal version
Complete Stage 5 in the Normal version
Complete Stage 4 in the Special version
Complete Stage 5 in the Special version
Complete the second cycle in the Special version
Complete the third cycle in the Special version
Finish the game with Jeeno in the Normal version
Finish the game with Beltiana in the Normal version
Finish the game with Iceman in the Normal version
Finish the game with Schneider in the Normal version
Finish the game with Alteeno in the Normal version
Finish the game with Olisis in the Normal version
Finish the game with Jeeno in the Special version
Finish the game with Beltiana in the Special version
Finish the game with Iceman in the Special version
Finish the game with Schneider in the Special version
Finish the game with Alteeno in the Special version
Finish the game with Olisis in the Special version
Complete the fifth stage without assistance in the Special version
Complete the game without assistance in the Normal version
Complete the game without assistance in the Special version
Complete stage 5 on a single credit in the Special version
Complete the game using a single credit in the Normal version
Complete the game using a single credit in the Special version
Complete stage 5 on a single credit without assistance in the Special version
Complete Stage 5 in Co-Op play using one credit each in either version
Complete the game in Co-Op play using one credit each in either version