Who wrote the parable about a man who was branded with an s for killing someone in his youth but led exemplary life which resulted meaning of being altered from sinner to saint?

The parable you're describing is likely not a traditional parable found in religious texts. There are many stories and tales about people who have committed sins but later become saints or lead exemplary lives.

However, the specific detail of a man being branded with an "S" for killing someone is not a common element in any known parables or stories. It's possible this is a modern reimagining or adaptation of a classic theme.

To find more information, it would be helpful to know:

* Where did you hear this story? Was it a book, movie, or personal anecdote?

* What is the context of the story? What message was it trying to convey?

Knowing these details will help determine the origin of the story and the author, if there is one.