Flash Thompson
In the Amazing Spider-Man #4 Peter Parker fights Flash Thompson and beats him. After that Flash only insults Peter.  Flash goes back to beating Peter up when he and Peter both like the same girl. Flash makes sure that his friends are with him to stop Peter from fighting back.  After leaving high school Flash and Peter Parker still hate each other but both get along with Harry Osborne who becomes Peter's best friend.  Flash later leaves the country to fight in the Vietnam War. When Flash comes back from Vietnam, he is disturbed by everything that happened there. Flash starts to drink alcohol to forget what happened and all of Flash's friends leave him, because he fought in Vietnam, except for Peter Parker. Flash and Peter become good friends after that.