Arabic: "Drop it now." As in, 'stop talking about this conversation topic immediately, please' but in as few words and with maximum urgency as possible. If it matters, the speaker is of a social rank beneath the listener, though he's anxious enough to give this order regardless. Both are adult male.
Persian: "You shouldn't watch." This can be slightly more polite, because the speaker isn't angry with the listener, he is trying to gently suggest that he look away before an unpleasant scene unfolds. If it matters, the speaker is of a social rank beneath the listener. Both are adult male.