Can't think of any games that I beat that I would consider hard at the top of my head, besides Dark Souls I guess.
I beat the original Zelda about a decade ago, and I thought that was a tough game.
Metro 2033 Redux on the hardest difficulty was also a bit insane at some parts.
"Just for comparison Uncharted 4 was 20x bigger than Splatoon 2. This shows the huge difference between Sony's first-party games and Nintendo's first-party games."