Breath of the Wild. I beat Ganon shortly after leaving the plateau, and never saw any of the story or very much of the world. It was just bad luck that I ran into Hyrule Castle and thought it was where I was supposed to go, possibly after selecting the wrong mission.
Now that I've beaten the game and found the end boss to be sort of boring and easy with only 6 hearts... I don't feel much of an incentive to go back and play the rest of the game. So I regret finishing it because now I feel like there's nothing to be gained from playing through anything else in the game.
Hoo, that's rough. Making the end boss available from a start is a unique idea, but with such a heavy side-effect; though, one that would be easily remedied with more compelling story segments, which (and I know this is debatable)
is possible in a nonlinear game.
I regret finishing Spyro: Enter the Dragonfly.... Especially to 100%. It was awful, even as a kid who thought that Spyro was the absolute best platformer mascot(yes, I thought Spyro was 100 times better than Mario back then)..... I mean. I sort of liked the new Breath abilities.... But man that game was hot garbage that repeatedly froze my PS2, making my progress constantly for naught..... Not only that, but the final boss fight was really terrible. I hated it.
It was the beginning of the end for Spyro as well. It is a shame. Because Spyro was lined up to be one of the greats.
I used to love Spyro. I think I played the original game on the PS1, not entirely sure. But I hate how braggy and snarky he got in the later games.
This really gets me thinking... is there any company capable of keeping a colorful mascot franchise running other than Nintendo? It seems like any other company either gets taken over by the cold harsh world of business (Rare/Banjo), fail to produce any critically acclaimed modern titles other than retro/nostalgia titles (Sega/Sonic), or just inexplicably don't seem to try (Capcom/Mega Man). Meanwhile, Mario, Kirby, Donkey Kong, and Zelda sell in droves. Yeah, the new-idea titles don't sell as well, but they're still critically acclaimed.