Suggestions needed: Open to anyone

So this is my first 'blog'. I'm not sure it's considered a 'blog' in the way blogs go, but oh well.
I need suggestions on how to resolve a conflict in a story I'm writing. I'd like a believable ending/resolution and I'm at a loss.

Here's the scenario-
Males X and Y are dating. Z moves to the town and goes to school with them. Y befriends Z with intentions of only being friends, but X can see Z is attracted to Y and becomes suspicious and jealous by the way Z is gazing starry-eyed at Y all the time. Y beats Z up and lies, he says Z initiated it. The story goes on and Y finds out that X was really the instigator of the fight and has been bullying Z all along and they break up. Eventually Y and Z begin dating, but the bullying continues.

What I want to write is the climax where they come head to head, but then how do I continue writing X in this story? Where does he fit in? Realistically he wouldn't just stop trying to break up Y and Z. Nor would he just fade out in the background. I have no clue what to do with him. I know I should have thought of this before, but honestly, I thought something would have worked itself out in my head already.

Like I said, I don't want to cheat the reader and kill him or send him off to boot camp or something just to get rid of him. I should say that Z does and has stood up to him with his sarcastic comebacks so he's no wimp.

Ideas are appreciated. I'll even mention you in the chapter notes for helping me out. Reply here or in a private message if you want to.

Thank you and have a great weekend!!! =)