I've never really been bullied, neither in school, university or work. When I realized that I thought that perhaps I was the bully if nobody bullied me. But I can't think of having bullied anyone either, at least not intentionally.
I replied to OP but I also need to say that I have definitely been the bully before. Very very inept coworker that after months of mentoring started to blame me for their short comings. So, after that, I stopped being so nice. There was only so much bullshit I could handle.
So at the time, it felt justified? But looking back I wish my response was to just ignore them.