I don't think this is the right place for this question, considering that this is a speedrunning forum. But I'll entertain it with my own hot take.
Lots of levels fall into the "so bad it's good" category. A level can have frustrating gameplay or strange design choices, but still have humour and charm in spite of that. Even if a level is really, really bad, that at least gives it infamy and as a result, makes them interesting. I kinda treat most levels like they are an "underdog" if that makes sense. I root for them, even if I don't always have the best time playing them.
In my mind, the true worst levels are the ones that contain offensive/explicit/triggering content or theming/messages. Unlike the "so good its bad" levels, these pose an actual risk.
Lots of those (unrated) levels exist online. If I can only pick rated levels however, I've narrowed it down to two. One of which is so graphic that it wouldn't be appropriate naming it here. The other having such a poor message that I refuse to call by its proper name: WMx4.
I won't be going into further detail on the level.
Edit: I also really like P0RTAL by Minesap.
imo any jenkins level sucks ass. i mean the deco is fine but the gameplay is horrible. i have experience with one of his levels and it was the most unenjoyable thing i have ever done
Jumper I don't know why just the upside down ship is hard for me
main level? the challenge. its so unchallenging that i bet i could do it blindfolded. but if were talking rated online levels then i think id have to go with square adventure or something. it gave me so much trouble when i was going for the map packs
I am extremely excited to announce that our website for tracking speedruns of rated user platformer levels is finally open!
This website was developed by ElohmroW, and I provided the finishing touches needed to get it up and runni