Just showing that you have the ability to strike back is often enough.
Oddly, became friends with my tormenter and had a lot in common.
Grandfather was right -- if you get hit, hit back, twice as hard.
As an adult the concept works. Bees can’t hurt me significantly, and even when they land an attack they die - but I go out of my way to leave them alone.
The trick is to turn off the switch in your head that tells you to stop if you're in too much pain or something is very wrong. Only real lunatics will keep going at someone that fights like that, and those are pretty rare.
When I went to highschool, someone in the class came up with a new nickname for me, despite much smaller than that person I fought back, I punched him as hard as I could, got badly punched back too. But after that, no one ever called me by that nickname.
When my son goes to school, I will tell him to fight back in case of bullying. It's the way the world works and if I had known that in middle school, I would have had a much better time and wouldn't have had thoughts of suicide.