Book where the world is a utopia teetering on becoming a dystopia. Bonus points if the main characters are wholesome and good, and the villains are dark and extremely evil.

I love seeing a world in a story that is worth fighting for. It really raises the stakes. I love it when who or what is being fought is incredibly dark. Any genre will work. I'm a big fan of the worlds of Star Trek and My Little Pony: Friendship is Magic. They are pretty much utopias that end up on the verge of becoming dystopias often.