に付け込んだ

took advantage of

→ に
phrase Rare #39,827
took advantage of Follows a noun describing someone's weakness, kindness, ignorance, or another vulnerability.
JA: 彼は相手の弱みに付け込んだ。
EN: He took advantage of his opponent's weakness.

彼は私の年の若い事に付け込んだ。

He took advantage of my youth.

彼女は私の無知に付け込んだ。

She took advantage of my ignorance.

ジョンはビルの弱みに付け込んだ。

John took advantage of Bill's weakness.

彼は彼女の親切に付け込んだ。

He took advantage of her kindness.