Here is the full list of all 15 SPLIT BULLET achievements.
Defeat 'Hexagonal'
Defeat 'Bad Squares'
Get killed for 10 times
Get killed for the first time
Run the game for the first time
Defeat 'Hyper Spin'
Defeat 'Trianglism'
Defeat 'Geometry'
Defeat 'Twins'
Defeat 'Surface'
Defeat 'Time'
Defeat 'Space'
Defeat 'Reverse'
Defeat every stages
Get killed for 10 times, with the record of 90%