If "vite" means "quickly" or "fast," the opposite would be "lentement" (slowly).
If "vite" means "soon," the opposite would be "tard" (late).
If "vite" is used in the expression "aller vite" (to go fast), the opposite would be "aller lentement" (to go slowly).
It's important to understand the context of the word "vite" to determine the appropriate opposite.