Looking for fictional books

I've recently gotten into reading. I realised how much I love fiction, and a couple of tropes. So I'm here asking maybe some of you know any books that have them.

I love it when the story focuses more on world building rather than character. The theory crafting I can do in my head, or just before I sleep, is priceless.

Here I'll contradict myself by saying a character development related point, but the more important one. I'd like to read more works that show some mysterious big-bad first as a rivalry, later as a friend. They soften up with the MC and we they become friends or allies or whatever. We get to see a BBEG of sorts's friendly and weak side. I get that it's a bit childish, but I lost my mind of how cool of a character they made the first time I read it. Now, it was in a manga, so I'd love to read an example that made this best or first.

Thank you in advance, even if you just name some genres or authors.