since it’s more than 3 characters, these will be short 

Sonic likes having a shorter girlfriend, it strokes his ego. But he’ll poke fun at her more often than he should tbh. He’s the one who calls his s/o a midget, and that gets old fast

Saitama doesn’t really care what they look like. They could be taller than him and thin as a stick, it’s just… appearance doesn’t compute with Saitama, if that makes sense. He doesn’t take notice until they complain about their height or weight some day. And he’s just kind of like “Oh…. yes. I see that.” So there’s really no difference when it comes to what his s/o looks like. I don’t see Saitama having interest in relationships, but if he actually found a s/o he liked enough, appearance obviously doesn’t matter. He’s not subjective when it comes to that stuff

Genos: Doesn’t mind at all. He doesn’t focus on physical attributes that much anyway. He’s basically a robot, so he can’t say much in that arena

Garou: Will honestly make little comments about her size sometimes. Less her weight and more of how short she is. That’s just how he is. If it offends her, he haphazardly apologizes, not really seeing the problem. He was just making observations

Metal Bat: He’s ridiculously defensive of her, even when it comes to her own opinions. If she makes a little comment about not liking her height or weight, even if she’s just joking, he goes off on these “There’s nothing wrong with the way you look! Don’t say that!!!” tangents