Would that be "Do all evil" or "Do exclusively evil" or "Do no good"?
evil(x) -> not(do(x)) which equates to not(evil(x)) or not(do(x)).
The negation would be evil(x) and do(x) by DeMorgan's law.
If what you mean is all(x), evil(x) -> not(do(x))
then the negation would be exists(x), evil(x) and do(x).
There's also the option of "Do Some Evil".