This guy doesn't get that I don't like him, and he keeps pestering me to hang out... please help!?

You don't have to be mean just be direct and be done with it. The next time that he asks or pesters you tell him something like "....look (Jim) although I appreciate you wanting to hang out with me but I have to say I don't really feeling comfortable hanging out with you but thanks for asking. If I change my mind I'll let you know until then please stop asking me." You're not being mean by being upfront with him and besides why are you more concerned about him being upset for an hour or two then you are about your feelings? You should be more concerned with and not stressing about the next time he asks you to hang out, just tell him and be done with it. If he continues to ask you after you directly tell him to stop asking, you can remind him of your conversation and then tell him to stop haring you.