These are several good phrases that may help to stop a bullying situation.
“Look, I don’t give a crap what you think about me.” and walk away.
“If you weren’t always telling everyone (place your own word here) about me, you might find I’m a decent person.” Walk away.
“Seriously? Is that the only way for you to feel good bout yourself? Make others feel bad?” Walk away.
“You aren’t even worth the effort of arguing.” Walk away.
“Don’t care.” Walk away.
The moral of this story…Walk away. If you stay, you are literally just giving the bully a chance to give you a sharp recoil. That’s not what we want. And if they try and drag you back in, don’t. If they follow you, get an adult. BUt don’t go right to an adult. Try it yourself the first two or three times, then get an adult.