I sent my teacher a bad email what should i do ?

Depends what kind a school you go to. also depends on who sees it. because if it is his school e-mail , he could get in big trouble because he is a teacher. And depending on what you said. But most likely nothing will happen , but if it does you have to deal with the punishment. You shouldn't even be scared because you made the decision on e-mailing him. so there should be no question what you should do . Deal with it, you decided to do it so don't be scared.