I want to learn how best to handle and manage a bully at work, who is as I described in the title, and without having to file a formal complaint to Human Resources?

I've read that bullies only respond to strength, and that if you show any weakness to them, they will exploit it further.

I don't know how to accomplish that.... ? I kind of cower to bullies and get intimidated and then end up apologizing when I shouldn't have to apologize.