expression, godan verb (-mu)
take advantage of someone's weakness; exploit a vulnerability
Used when someone deliberately exploits another person's weak point, often in a negative or manipulative way. The expression is a set phrase combining 弱み (weakness) and 付け込む (to take advantage of).
彼は人の弱みに付け込んで金を巻き上げる。
He takes advantage of people's weaknesses to swindle money out of them.
弱みに付
Please stop doing things like exploiting people's vulnerabilities.