I think Hollow Knight, in terms of most recent games I've played (and am still playing). Like some others have said, the base game is challenging enough, but some of the optional stuff is absolutely nuts.
I've really enjoyed the game so far though, and I highly recommend it if you like platforming, challenges, story, and have a lot of patience haha. I can see if you're more of a casual gamer the game might not be for you, or if you get frustrated easily because the game definitely tests your patience every now and then. If you can get past that though the game has a lot to offer and is definitely worth picking up!
I was gonna say Cuphead but I only completed the first world and haven't played it in over a year
I definitely need to get back to it eventually but I think juggling that with Hollow Knight would be a recipe for disasterl-lol
I was gonna say Cuphead but I only completed the first world and haven't played it in over a year
