I wouldn't say I have a controversial pairing 'type'-- whether it's a ship between enemies or between two villains or what, I have to find the individual example compelling, and there's a lot that I just don't care about.

I have always shipped Doc/Marty from Back to the Future, which has an... extremely variable age gap? Or no age gap if you go with the video game timeline? But the thing is it doesn't fit into a controversial 'type' because it's NOT a mentor/mentee relationship, it's just best friends where... one of them happens to be an old guy.

(as an adult, my feelings are... different, than when I was a kid. Like, I don't see Doc going for it while Marty is underage, which was not a consideration I even took into account when I was young, just because as an adult if I connected on a mental/emotional level with someone young and they came onto me, I would pump those brakes hard. BUT taking the video game into consideration then you have a whole time traveler's wife thing, which I think is compelling!)