The story:

A young couple is about to go through a wedding in the middle ages. The young man feels like he's on top of the world. But just as he's about to go through his vows, he's arrowsniped to death. Later we learn that it was done by a guy who had nothing but pure hatred for the young man. Realizing that the person he had killed will probably be "reborn" into the world, he sells his soul to the devil for the ability to track down the soul when it is born into the world so that he can kill it as well as for the eternal youth and immortality he needs to make sure he can keep on doing it just for the sake of his hatred. Why so much hate? I could probably explore that, but given that the man is insanely obsessed with making sure the focus of his hate never has a full life, well...

And the story comes to the present day when he's born again for the thirteenth time, but this time he's got a guardian angel watching his back.

This isn't too generic, is it? Or too cliche'd? Or something?

It's a little crazy, and could turn out cheesy if you're not careful, but I love it! I think it's a great idea, and I've never read anything like that, so as far as I know it hasn't been done before.

I think you should do it, just be careful about it turning cheesy, like I said before. As long as you make it very clear that the killer is completely insane (Perhaps he goes mad after killing the guy the first time?), you should be able to avoid it being cheesy, also make sure that when he sells his soul to the devil that bit doesn't turn cheesy either, I think you have to try and make that bit quite creepy and dark. I think those two parts are the bits that are in danger of seeming cheesy, I don't think you should have any problems with the rest.

Good luck! I'd love to see this :)

Wow. If he hates the guy that much you'll need to give him a really good reason. Like maybe, in another past life, the guy at the wedding was an evil motherfucker who killed the hate guy's family? Except that would cause some plot holes that you would need to smooth out. Also, the existence of the wedding wouldn't serve any purpose unless you want the bride to play a further role. Which might actually work, like she's the "guardian angel" who learned about the killer's motives and actions and is trying to get to her husband in his new life before the killer does. I dunno. It's your story, so your call.

I love angel-demon stuff.

Just make sure you research your theology and philosophy and get it right. That's a plus.

That sounds mega cool! I agree with Hunchdebunch though, don't let it become cheesy. Maybe when he sells his soul, he has to scratch in his own skin "MY SOUL IS YOURS" or something, and he forever carries that scar. It could be cool. Also I think you couldn't have him killing the guy 20 times before anything greatly significant happens. And, I think, you would need something significant to happen, because otherwise there wouldn't be much interest in the story. Know what I mean?