Most of these comebacks are absolutely terrible. Here's a few that I use regularly. No you shut up, you'll never be the man your mother is! Why don't you slip into something mais comfortable, like a coma.
I would say something intelligent, yet cutting to the soul.
'Firstly, you have no way of making me shut up. Secondly, if I obeyed the command of every idiotic troll on the internet, you wouldn't be here talking to me now. Yet another idiot that talks before they think, that opens their trap and comes up with yet another reason why people are stupid...'
i just say " sorry i don't think i can shut up if a piece of trash is in my face" or well there was this one time in 5th grade where my besties bf was not being a good bf and he thought i liked him so he hated me and he went " well VK why don't you just shut up and mind your own business.'" and you bet i said " Motherfucka I dont think i cant shut up if there's trash in my face" i was a savage 10yr old FML
Just say "Okay Boomer..." its quick and insulting.
or just start cantar "and dance with me, this women is my destiny" that's the only verse i know. if your a girl you don't have to sing that verse
typically all you have to avoid saying is anything related to anger, like swearing. people will make fun of you for that. oh and don't say a very long come back that will lose their interest or make them think that you are putting to much effort for such a little small phrase.