Dimmesdale was only able to forgive himself for what he had done minutes before his own inevitable death. He forgave himself and found himself worthy of asking forgiveness of the people he had kept the secret of his adultery from only then on the scaffold.

Does Dimmesdale confess his sin to Chillingworth?

Not only does Dimmesdale confess, but he must do so alone. Although Hester helps him to the scaffold where she was punished seven years before, she cannot help him make his peace with God.

How does Chillingworth get revenge on Dimmesdale?

Chillingworth figures out that it is Dimmesdale who got Hester pregnant, and who’s the father of Pearl. He wants to get revenge on Dimmesdale. He tortured Dimmesdale by making him feel guilty.