Is it possible to legally threaten someone. is so how?

im a minor. the other person is an adult of the age of 19, my best friend who happens to be a female was headed by him and broke her nose. this was because of a fight they had. she was 17, she has that thought process that it was her fault when it wasn't. so i want to send him an email that legally threatens him, for my family is a politically powerful family capable of just about anything. now that you know the position im posed in i would enjoy a comment from someone with LEGAL jurisdiction or legal training. All in accurate comments will be forwarded to a moderator.