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'm the kind of person who has no issues with moving on from a game with only 20% of the achievements/trophies unlocked after beating the final boss. If it's not fun, it's not fun.
I think the only two games I set out to 100% were probably Super Mario World, or Donkey Kong Country 2.
Ah dk3, the one I've NEVER beat. I always set out to do it and grow bored first. I think by the time I started playing that really good games existed like halo and the like.