The Transformation of Macbeth
From the beginning of the play, Macbeth undergoes a complete change in character--from a virtuous nobleman into a monster. He has a tragic weakness--ambition--which, when released, draws him into a web of evil and corruption that finally leaves him with none of the noble human qualities he possessed at the beginning of the play.
Before being transformed into a murderous monster, Macbeth is a model Scottish noble. He shows great loyalty and devotion to both King Duncan and his country in his fight against the Scottish rebels. He also fights with great courage, which he draws from knowing that he serves a good and virtuous cause. He is modest when confronted with his achievements, in contrast to the arrogance that he displays after becoming king. He loves Lady Macbeth, an emotion he will eventually lose by the end of the play. Most of all, he fears what his greed and ambition can lead him to become, and he feels dubious about acting on them.
Macbeth takes his first step toward becoming evil when he is confronted with the knowledge that he will be king. When the witches tell him "All hail, Macbeth! that shalt be king thereafter!" he makes the mistake of letting his ambition overrule his judgment. If his judgment had remained intact in the face of the witches' powerful prophecy, he certainly would have decided not to let his actions be dictated by a prophecy given to him by three strange witches who evade most of the questions he asks. With great trepidation and considerable pressure from Lady Macbeth, he commits his second mistake by proceeding to murder King Duncan. Driven by a persecution complex that starts with the knowledge that Banquo is meant to be the father of kings, Macbeth sends out thugs to assassinate Banquo. This takes Macbeth even beyond the murder of Duncan; it demonstrates that he will spare no one--not even a close friend--to secure his illegitimate kingship. From here, it is easy for him to continue sinking deeper into evil by later having Lady Macbeth and her son killed. Shortly after the murder of Banquo, the dead noble appears at Macbeth's feast. The terror of seeing Banquo's ghost makes Macbeth more paranoid and insecure than ever, which leads him to seek answers from the three Witches. After watching the apparitions and learning that no woman-born man can harm him, he repeats his earlier mistake of believing the prophecy. When Malcolm and Macduff lead an army into Scotland, Macbeth believes he is invulnerable and has no reason to fear them. This mistaken belief in his invulnerability leads to his final destruction when he is confronted by Macduff. He scoffs at Macduff's vow to kill him, thinking such an attempt is futile, so he is completely unprepared to hear his nemesis...