Fascinating insight into how people think.
Beating up the guy may feel good for a little while, but it puts you in the wrong and carries a substantial risk to both of you. The other silly things mentionned like screwing his wife or daughter are just fantasy like you see on a bad soap opera.
But letting it go is difficult; it can eat away at you even though you might want to take the higher ground.
Being the target of a bully was a terrible, long lasting fear. Judging from the comments in this thread, many people have turned that fear into anger, which still eats at them. So, you've got to not just let it go, but confront it so that it doesn't bother you anymore. You have to prove to yourself that you have it within you to stand up to your worst fear.
The first thing is to acknowledge his existence. At a time and place of your choosing. Don't be threatening. That's important.
Expect his reaction to be a surprise to you, because the reasons why a kid would bully others are very, very complex. Watch his eyes. He may have forgotten you completely, or he may be sorry, or fearful, or he may have enjoyed it and look forward to more.
If he is not interested in bullying you more, then you're done; you confronted your fear, and it melted away when you did that. Most kids grow out of being a bully. Some don't.
The ones that don't are particularly dangerous; Mike Tyson said he had so much pain inside of him that the only way to make it go away for a little while was to hurt someone else. Badly. You don't want to get into a fight with a guy like that.
So the odds of him responding to a civil conversation in a hostile manner are actually quite low, but you have to expect that it may happen. Don't arrange to meet later, or get into a name calling yelling match. If he wants to fight, confront him immediately. Queity. Stay in control. Tell him to bring it on right now. Remember, this is about you confronting your fear, and has nothing to do with him at all.
You don't have to beat the crap out of him; you just have to not back down. If you are winning the fight, you can stop anytime you want. (And you should, to maintain you own sense of moral rightness). So what if you lose the fight? It means that you're not as good at a physical fight as he is. But you stood up to your fear.
The odds are you won't have a fight.
Most guys just let the fear and anger eat at them all their life.