I'd say Celeste, Hollow Knight, and Getting Over It with Bennet Foddy. Celeste gets brutal with the later B sides, C Sides, and Farewell, but it's a good challenge that feels amazing to get through (just beat Farewell this week and got 1a dashless, goldens are up next.) Hollow Knight is definitely challenging as you encounter new things, but nothing ever seems totally out of reach and the game does a good job of finding a way to let you get past those challenges (although the final Pantheon is currently kicking my butt lmao.) And then Getting Over It is, well, yeah. It's certainly the most rage-inducing one on the list, but I find it fascinating since it's essentially built around the struggle since every new inch of progress feels amazing, even if you lose it just a few seconds later. It's essentially creating true obstacles for you to figure out how to overcome with a real risk of setback and failure to learn from (as of writing this I have not completed the game yet, these are just my thoughts on what I've experienced so far.)