was ich getan hatte

what I had done

→ was
phrase Rare #40,989
what I had done Introduces a clause referring to something the speaker had done before another past event.
GE: Sie wusste nicht, was ich getan hatte.
EN: She didn’t know what I had done.

Ich schrieb alles auf, was ich getan hatte.

I wrote down everything I had done.

— Oldboy (2003)

Ihr Steuermann brauchte zu lange, um zu begreifen, was ich getan hatte.

Your helmsman took too long to understand what I had done.

Niemand wird mir glauben, wie leid es mir tat, was ich getan hatte.

No one will believe how sorry I was for what I had done.

Er wußte noch, was ich getan hatte.

He still knew what I had done.

Es tat mir sehr leid, als mir klar wurde, was ich getan hatte.

I was very sorry when I realized what I had done.