As noted, “that’s ever been completed by a human”. Otherwise there’s simply no ceiling; I can just create a game that requires you to perform 10 frame-perfect inputs every frame for five months straight and say “now I have the hardest game since it’s technically possible to win; checkmate.” With user-made levels, there’s still a ceiling defined by a human actually completing it, and I don’t think the human-beaten Mario Maker or Trackmania levels touch the extreme levels of difficulty at the highest skill levels of GD.
TL;DR: I think if we include user-made levels ever beaten unassisted by at least one human, Geometry Dash wins.
I’m pretty sure the trials of death in super mario maker wins.
Over 4000 hours over 7 years just to beat one level.
Do we have any evidence, though, that ChainChompBraden was exceptionally skilled and well-practiced going into this? Because to my understanding, the level ID for Trials of Death hasn’t yet been made available, meaning Braden is the only one who was able to attempt this. Meanwhile, Tidal Wave was and has been available for literally anyone, and despite being the most prestigious level in a game where people pour tens of thousands of hours into beating near-impossible levels, it’s only been beaten by two other people since it was verified last year, and these are the three best players in the game each with several tens of thousands of attempts on this level (they have god knows how many tens of thousands of hours of practice from other levels of similar but lesser difficulty).
Kaizo Mario can introduce some complexity that GD can’t by having more than one type of input, but GD’s hardest levels are so insanely precise (Mario Maker’s 60 FPS or anything even near it would render top-level GD play essentially impossible) that even though these both push the limits of what humans can physically achieve, GD seems more difficult at its highest level of play.
