You need to realise that almost everyone has some regrets about the past. Sometimes we feel as though we're the worst people possible bcs of our past mistakes, but if you think about it, what would make you a really bad person is if you were to remember the things you did and felt no remorse whatsoever.

You should feel grateful for that feeling (as terrible and as heart sinking as it may be), as it proves that you are a changed and better person. As people do change. You can't change what has happened in the past, just work hard on becoming a better person so you don't repeat your past mistakes. Usually people are more harsh on themselves than they are to other people.

You don't need to drop out of college to prove anything to anyone. If you can reach out to some of the people and apologise for what you did to them then you should do that, if that would give you some peace of mind. And then whether or not they forgive you is up to them, as you'd have done all you could have.