YOU SAID:

The worst thing that I ever did was what I did to you

INTO JAPANESE

私が今までにした最悪のことは、私があなたにしたことだった

BACK INTO ENGLISH

The worst thing I've ever done was what I did to you.

INTO JAPANESE

私が今まで行った中で最悪のことは私があなたにしたことでした。

BACK INTO ENGLISH

The worst thing I've ever done was what I did to you.