Here is the full list of all 21 PAIN: Below Sanity achievements.
Spin-counter: 1000x
Touch the very last water-trap.
Finish the 1st World.
Finish the 2nd World.
Finish the 3rd World.
The End.
Finish [PAIN] without any deaths.
Finish [HARDMODE] without any deaths.
Reach max. Speed.
Reach max. Size.
Yeah, right.
Finish all Achievements.
Enable EASYMODE.
Deaths: 150x
Deaths: 300x
Finish [PAIN] normally.
Play the waiting-game.
*turns into a claymation reference in 1 HOUR*
Play the game in under 30 minutes, then go outside lol
Resets: 25x