Can’t believe Celeste is so buried in a thread about platformers. It’s challenging but never unfair (game mechanics even weigh in the player’s favour, e.g. coyote time). A common complaint about difficult platforming is the brewing impatience from having to constantly restart, but Celeste’s reloads are so fast that this becomes a non-issue. Other than C-sides (and maybe some rooms in the hotel level), levels are small enough that you don’t have to slog through everything to get to the failure point.

Celeste is masterpiece tier for me, and I highly encourage anyone who remotely loves platforming to give it a try.