en_tn/1ti/01/16.md

I was given mercy

This can be stated in active form. Alternate translation: "God showed me mercy" or "I obtained mercy from God" (See: rc://en/ta/man/jit/figs-activepassive)

the chief

"the chief sinner" or "the worst sinner." Paul is saying that he has sinned more than any other sinner, not that he has been the leader of a group of sinners. See how you translated this in 1 Timothy 1:15.