Hi Shy....
It's important to recognize that this individual must be hurting inside to be acting out in this manner and treating others in such a disrespectful and antisocial manner. Sometimes when individuals are experiencing painful emotions, they don't know how to cope with them and process them in a healthy manner - so they engage in negative behavior such as picking on others and trying to get others to experience similar emotions that they themselves are struggling with. It's not an excuse for his behavior, just an unhealthy coping mechanism. By internalizing the awareness that this individual has 'issues' and must be struggling/hurting in some manner - you can try to develop subtle feelings of sympathy/empathy for him - and this will help you diffuse the emotions of anger & frustration that might otherwise surface due to his behavior towards you.
Please don't take what he says to you personally (I know that's a challenge in and of itself). His insults are merely an attempt to get under your skin - and not an accurate reflection of how others view you nor how you should view yourself. Generally speaking, physical appearances are superficial and our society is very misguided in encouraging individuals to place so much value on external appearances. We are all going to grow old and leave these physical bodies behind one day so there is no sense in growing too attached to them - you know? The real value lies within you and is expressed through your character attributes and your ability to exemplify and express love, forgiveness, kindness, empathy, selflessness, integrity, etc. Don't let anyone ever try to convince you otherwise.
If you try to engage in making 'comebacks' to this individual you will be playing his 'game' and that type of response will likely only provoke him into continuing his behavior. Due your best to avoid/ignore him as best you can. Look at it as a challenge and remind yourself that his words/insults are empty and meaningless because they are only a product of his attempt to elicit a response from you and a reflection of his unhealthy internal situation. If you struggle with doing this other things you can do is ask the teacher in private to have your seat changed so that you no longer sit in the vicinity of this individual. I don't see why a teacher would not be open to taking this course of action having knowledge of what's going on. If the teacher is unresponsive and you feel this enviroment is affecting your ability to concentrate in class - consider consulting with a Guidance Counselor at your school, someone who can intervene on your behalf and help resolve the situation.
Hang in there. You'll get through this challenge in your life.