What is the most difficult piano piece to play?

There are many classical pieces that are from the baroque age (approx. 1500s-1600s) that are very difficult due to their heavy reliance on the technical ability of the player. Some of these include La Campanella, by Franz List, which is heavily regarded as the hardest piano piece of all time. However, there are different meme songs, like Rush E, that aren’t registered songs, that deem themselves to be extremely hard, due to the amount of notes you have to play, and the speed you are required to play them at. However, this song dwarves in comparison to the other more classical pieces that are way more technically challenging and ask more of the piano player themselves.