unacquaint means to undo (one's or someone's) acquaintance (with someone or something). Lexicurio rates it Rare gem — a strength score of 80 out of 100.
Etymology
From un- + acquaint.
verb
- To undo (one's or someone's) acquaintance (with someone or something).“he […] is a scoundrel, and I'm going to unacquaint myself with him.”