Phrase for "not to Mention" or "leave in Peace"

Word Meaning:

LET ALONE — (idiomatic, chiefly in the negative) Much less; to say nothing of; used after one negative clause to introduce another, usually broader and more important clause, whose negation is implied by the negation of the first. However either of these instances mentioned can be applied with the use of let alone.

Definitions from Wiktionary.