What should I do if I meet someone I hate?

When you meet someone you hate, you'd better stay away from it, just don't go near it. Keep a certain distance from others.

If you can't get rid of him, really bother him, nothing can't be solved by fighting. If there is, just twice.

But personally, it is best to stay at a respectful distance from others. As the saying goes, dogs can't bite back.