How do you deal with people who don't like you without a clear cause?

In High School there was a guy who did't like me. And it was for no apparent reason at all. I was kind and polite to him like I was to everyone else. And when other people talked to him, like one guy who was even an asshole to girls, he was happy and talkative. When I asked him something he answered shortly and looked annoyed or like something bothered him.

The only thing I can think of is that people have often called me a very attractive and handsome guy and that some have thought that I am a bit soft or like feminine in a few ways.

How do you deal with people who don't like you without a clear cause?