Not sure what the hardest was for me but Scarlet/Violet have by far been the easiest for me. There was literally no challenge at all.

I don’t know if I found an exploit, but I think I beat the Elite 4 of Sword and Sheild with 1 Pokémon.

Ice Darmantian with either choice scarf or the other choice for attack.

Literally 1 shot everything. It was also drastically over-leveled