In The Scarlet Letter Hester's sin played a big role story.  Although many characters were affected by Hester's sin, Dimmesdale was most affected.  Some reasons are that Dimmesdale was forced to hide his sin, he became very ill, and he became obsessed with making up for his sin.  

    Arthur Dimmesdale had to cover up the sin that he committed.  He kept the secret inside of him and told no one.  Hester had to wear the scarlet letter, but people eventually accepted it.  Dimmesdale, on the other hand, kept his sin inside and people were unable to see the turmoil he was feeling.

    Dimmesdale became very ill because of his wrongdoings.  His health continued to fail throughout the story.  Hester's sin affected everything he did in his life.  He could not do anything without thinking about his sin.  This caused his health to deteriorate.

    Dimmesdale wanted to make up for his sin.  He wanted to be forgiven for the sin he committed.  He did not eat or drink for days at a time.  He flogged and beat himself and went on all night vigils to atone for his wrongdoing.  He tried to tell his congregation that he was a sinner but they just thought he was being humble.  This caused him more pain.  The only way he could relieve himself was to tell people and hope they accept it.

    As anyone can see, Arthur Dimmesdale was most affected by the sin's of Hester Prynn.  Some reasons are that he could not make amends for his sin, he became ill, and he had to hide his sin inside himself.  In conclusion, Dimmesdale was the character affected most by Hester's sins.