Honestly...as an employer, if you came to me and said so and so is doing this and if he starts something I will finish it...I would see you as no better than him. Ya know?

I am a firm believer in fighting is wrong. There are better ways to solve things. It sounds like your coworker is a young punk (ohhhh and there are many). I think you are right in going to your superior. However, I would make it clear that you do not want to bring violence into the workplace and would like a peaceful resolution to this situation. Then slip in, as an afterthought even, that if the situation does get out of control you may have to defend yourself.

Many employers will not tolerate fighting. Even if "he starts it", you may still be punished for participating. Lots of kids at work say that, "oh he hit me first". The school doesn't care. Each person is equally guilty if both are engaged. The only way you are not guilty is if you don't retaliate. Frustrating, yes. It's called a "No Self Defense" policy.

What about a restraining order? Since this person is obviously harrassing you? I think I know where you are coming from. Being bullied is frustrating and hurtful. Wanting to inflict harm back is normal. But think through the situation. Play out the "what-if" scenarios. Ultimately, do what you have to do to protect not only yourself, but your job. Don't act rashly.

Good luck!