On the Cross, for whom did Christ pray?
Answer: “Father, forgive them, they know not what they do.”
As St, Stephen is being stoned, what does he say?
I don’t have the exact words but he prayed that their sin of killing him would be forgiven.
Just a couple of examples from the Bible for you.
Many martyrs pray for their persecutor’s forgiveness as they are being executed.
I do not deny any of that, but it is still not payment for another’s sin when a sinner prays for his fellow man. Its forgiveness of the highest order though.