The second game I ever 100%ed was Arceus and I still can’t stand the thought of picking it up again, years later. The first game was Horizon Zero Dawn, which is still fun.
I just got 100% on Nier Automata, and I only loved it more as I played it more. Usually I hate any grinding in any game and will either skip any content that requires grinding, use mods to bypass it, or just put down the game and move on to another one. But the whole game just felt so damn good. I could just walk around for hours doing nothing because the movement felt so good.
There was quite a bit of grinding, but I didn't find any of it too bad. I got 100% in about 50 hours, which is my sweet spot. Any longer and I feel like the game is dragging on.