I think you should know what the censored text is ;) Back on Mountain (By MaJackO) is probably one of the most unenjoyable levels i've ever played. And i suffered through it after 4 94% deaths. I know it's an old level, but it's so unbalanced and unfair. Jawbreaker (By ZenthicAlpha) is my second hard demon, which was much better. The gameplay is okay, but some orb buffering causes unfair deaths. Cant Let Troll (By Defectum), is just a memory level. The most annoying part is the beginning with a key that kills you. Triangle Out (By MaJackO), Is probably his best level. It only has a few unfair timings but overall it's pretty good for it's time.
Images created by me. Based on my ingame icon and the default icon.