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