Well I guess the first thing you need to do is ask yourself if you want to go to prom with this guy. Since you don't seem to like him and are even kind of scared of him, I suspect the answer is no. But are there any other factors? How do you feel about going dateless if it comes to that? Is he "scaring" you enough that you're worried he'll react violently if you cancel? There's nothing wrong with backing out of your prom date with this guy as long as it's well thought out and you do your best not to hurt his feelings. He may object by saying that's not allowed or not nice or something, but you are definitely within your rights.

Prom is so full of tradition and social expectations that there can be pressure to be a certain way. But it's up to you how you want to spend your own prom, and while there is no guarantee of a good time no matter what you choose, going with a date you actually don't like sounds pretty awkward.

Then again, don't forget that you CAN have a date with this guy if you want to. And you can do it on your own terms. You don't have to go anywhere with him afterward and you don't have to spend prom by his side even if you are his date. If you do go together, you might want to remind him that you're going as friends.

If you decide to cancel on this guy, I suggest doing it as soon as possible. If he's set on going with a date, that will give him more time to find somebody else. For tips on the actual cancellation, you might want to check out this slightly related advice on letting him down easy.

Either way, if this guy continues to actually scare you, I suggest sharing your concerns with a trusted adult.