Between the beginning of the play and the end of Act 3, Macbeth undergoes significant changes in his character and mindset. The most accurate assessment of his transformation is:
c. He no longer hesitates to use betrayal to get what he wants.
At the start of the play, Macbeth is depicted as a valiant warrior who is hesitant and troubled by the idea of murdering King Duncan to fulfill the witches' prophecy. However, by the end of Act 3, he has moved past his initial doubts and trepidation, using deceit and violence, including the murder of Banquo, to secure his power. While options b and d may have elements of truth, c most distinctly encapsulates his moral decay and willingness to embrace betrayal as a means to an end.