A had a lot of trouble beating games growing up, but it's rare that I find a game overly hard these days.
Tales of Graces F...as much as I love this game, I can't beat Kurt for the life of me. I'm pretty sure he's considering pretty OP anyway.
Honestly that is the only game that comes to mind. But, I'm sure some older SNES titles I'd find pretty difficult if I were to give them a go.