How does Shakespeare convey the changes in Macbeth throughout the play?

Macbeth is about a man who changes from hero to villain. In the first act, both the ominous witches and a group of soldiers mention Macbeth. The king refers to him as noble, and the men describe his brave--and bloody--feats on the battlefield. We first meet Macbeth when he and Banquo come across the witches. They tell him he will be thane of Cawdor and king. Banquo marvels at the news, but Macbeth wants to know more. His curiosity is evident and possibly foreshadows his later behavior. Once granted the title thane of Cawdor, he immediately starts pondering the horrible possibilities of how he could become king: “The Prince of Cumberland! that is a step / On which I must fall down, or else o'erleap, / For in my way it lies.”

Lady Macbeth describes Macbeth as being ambitious but “too full o' the milk of human kindness.” He expresses reluctance to assassinate his king, but Lady Macbeth convinces him to proceed. This demonstrates that Macbeth does have a conscience--he struggles with it throughout the play--but his desire for the crown overcomes his compassion and sense of honor. He kills King Duncan and suffers terribly for it, stating, “To know my deed, 'twere best not know myself.”

After Duncan’s murder, Macbeth sinks further into bloodshed and paranoia. He slays the king’s guards, whom he and his wife framed, and proceeds to kill Banquo and attack Fleance, who escapes. The Macbeths are afflicted by “terrible dreams / That shake us nightly.” Macbeth cannot rest in his power for fear of it being taken away. He further consults with the witches. His trust in these forces of fate and darkness reveals how far he has come, from curious skepticism to absolute faith. The witches refer to him not as a hero but as “Something wicked.” After speaking with them, he decides to massacre Macduff’s entire household, including his wife, children, and servants.

By the time Lady Macbeth dies, her husband seems completely numb. He merely remarks, “She should have died hereafter,” before giving a monologue about the pointlessness of life. Still, he believes himself to be invincible. At the end of the play, the once great Macbeth has become an egomaniacal, manipulative, and bloodthirsty man who has lost his love of life.