Rev. John Hale changed from bad to good. Although he was a reverend from outside of the village, he came in with an arrogant belief that he was to be the savior of this town. He coerced accusations from the girls until they listed names just so that the men would stop asking. Throughout the 2nd and 3rd acts, he sought ways to help get people accused. Both of these last instances may have been out of his own naivety, nonetheless, it was negative.
By the end of the 3rd act and throughout the 4th, John longed for a righteousness that would keep good people alive. He was of the belief that there may have been justifiable reasons to lie to the magistrates and that was just to ensure people would live. He worked tirelessly to coax confessions for this reason. However, he knew those in jail to be innocent. He plead on their behalf, but the magistrates would not listen. He confessed he knew that all of what had occured was wrong. It is good, even under duress, to seek righteousness and goodness.
Elizabeth Proctor is known for her ability to be cold to her husband. She too goes from bad to good. From prior to the start of the play, Elizabeth was having a cold shoulder toward her husband. This drove him into the arms of their servant Abigail. Elizabeth continued to hold that against John even into Act 2. They after John had let Abby go, Elizabeth still refused to forgive him.
By the middle of Act 4, Elizabeth and John have a discussion in which she confesses her coldness admitting driving her husband away. Then, at the end of the play she honors him by letting him make his own decisions about his life and by recognizing his goodness in death.
John Proctor also goes from bad to good. From being an adulterer to dying for his faith, Proctor grows from the beginning to the end. Proctor's character is careful to demonstrate the heart conditions of forgiveness and grace while living outside the regulatory rules of religion. His character demonstrates how much greater man can grow when not confined, but free to live in relationship to a higher power.
Mary Warren goes from good to bad in Acts II and III as she agrees to testify honorably in favor of the Proctors, but turns bad when the girls mock her in Act III.