Here is the full list of all 16 BIT.TRIP VOID achievements.
Collect 10,000 black Beats
Race against the Id boss for 2 minutes before beating the level
Turn all enemy Voids black and collect them during the Ego boss battle before beating the level
Watch the hidden cutscene
Beat Super-ego in Normal difficulty
Chained 200 Beats
Beat Ego in Normal difficulty
Beat Id in Normal difficulty
Register a high score on the leaderboards
Collect all black Beats without hitting any white Beats during a Challenge
Escaped Nether Mode
Chained 100 Beats
Chained 500 Beats
Beat the game in one sitting without getting a Game Over
Play through an entire stage in Ultra Mode in Normal difficulty
Defeat the Super-ego boss without getting hit by a white Beat