When a couple isn't fetishized.
That said, I like it when the characters have completely different personalities. Not polar opposites if that makes sense. They have something in common, but that's something the readers have to figure that out. It makes the reader go "what makes them love each other?".
I've said it before, but I love it when a character BRINGS OUT personality traits of their loved one that you didn't think they'd have. Like they're the only one to get them to laugh at something you'd never think they'd laugh at, but when you re-read the story you're like "No wait! THAT MAKES SENSE! THEY WOULD LAUGH AT THAT!".
That Stick Figure Isekai does it. Not sure if I wanna spoil it, but we are getting to this couple who does what I mentioned lol.