Here is the full list of all 8 One Final Chaos achievements.
Reach Paragon Level 1.
Reach Paragon Level 8.
Set foot on a unique landmass.
Unlock secret game mode #1 by dying in every possible way.
Unlock secret game mode #2 by □□□□□□□ □□ □□□ □□□□ □□□□□□.
Survive for at least two minutes in any game mode.
Survive for 30 seconds in every game mode.
Challenge the ghost of a friend.