How do you say opposite in french?

The opposites for the verb "venir" (to come) are "s'en aller" (to leave, to depart) or "partir".

Opposites of "je viens": je m'en vais, je pars.

- of "tu viens": tu t'en vas, tu pars.

- of "viens!" (imperative mood): "vas-t'en ! Pars !"