In The Scarlet Letter, Dimmesdale was the one who committed adultery, but he is seen as a better character than Chillingwoth. In what ways?

Unlike Chillingworth, Arthur Dimmesdale was an introspective person who continually examined the state of his own soul. Betraying his spiritual beliefs and moral principles caused him great shame, grief, and guilt. Dimmesdale came to loathe himself, not only for his initial sin but also for his weakness in not acknowledging it before God and his parishoners. Arthur longed for salvation and blamed no one but himself for his suffering. He bore no malice toward any other human being. He felt a special contempt for his sins because he was a minister, always aware of his spiritual responsibilities to his congregation. 

We can infer that Chillingworth examined his own sins and attempted to atone for them at the end of his life because he left his lands in England to Pearl before he died. However, throughout the novel he sought to salvage his wounded ego as Hester's humiliated husband by revenging himself upon her partner in sin. His revenge was cold, deliberate, and obsessive. He took joy in Dimmesdale's suffering. And unlike Dimmesdale, Chillingworth felt no responsibilities to his vocation; he violated without hesitation the most basic principles of being a physician. He used his skills not to relieve pain, but to inflict it--not to heal, but to destroy. Dimmesdale was morally weak, but Chillingworth was morally corrupt. He chose to violate "the sanctity of the human heart."