Don't come again.
Nidoto kuru na.
never again (with negative verb)
to come (spatially or temporally); to approach; to arrive; to come back; to do ... and come back; to come to be; to become; to get; to grow; to continue; to come from; to be caused by; to derive from; to come to (i.e. "when it comes to spinach ...")
(sentence end, mainly masc.) indicates emotion or emphasis; (used with masu stem verb) command; (used with dictionary form verb) prohibition