Here is the full list of all 15 O.C.D. - there are On Completeness & Dissonance achievements.
Complete the first 30 levels.
Get 20 3-point ranks.
Beat 10 levels on the first try.
Fail a level by electrocution for 10 times.
Fail a level by falling for 10 times.
See 10 blue screens.
Fail a level for 5 times.
Complete the sixty levels.
Beat the game without skipping levels.
Get 3 stars in every level.
Fail a level by bomb explosion for 5 times. (Requires DLC)
Fail a level by falling on spikes for 5 times. (Requires DLC)
Fail a level by falling on slicers for 5 times. (Requires DLC)
Complete 90 levels. (Requires DLC)
Complete all 120 levels. (Requires DLC)