In Shakespeare's Macbeth, Macbeth is a tragic hero. Aristotle defines the hero as a great man, who dies due to a tragic flaw, and his death is his own fault.
To begin, Macbeth is a great man—meaning he is "accomplished." In battle against Norway, Macbeth proves himself by showing admirable valor, fighting for his King and country (Scotland). In Act One, scene two, the Sergeant reports how brave Macbeth was in battle:
For brave Macbeth—well he deserves that name—
Disdaining fortune, with his brandish'd steel,
Which smoked with bloody execution,
Like valor's minion carved out his passage
Till he faced the slave... (18-22)
Without fear for his safety, he throws himself into the midst of danger until he faces his enemy. Duncan is well pleased and rewards Macbeth—with promises of more to come.
However, there are three witches who have decided they will trick Macbeth into sacrificing his soul to the powers of darkness—he will do this by killing the King. The witches meet him in scene three. They greet him by his present title (Thane of Glamis), and then they call him "Thane of Cawdor," a title that puzzles him for there already is a Thane of Cawdor. Finally the witches predict that Macbeth will one day be King.
All hail, Macbeth! hail to thee, Thane of Glamis!
All hail, Macbeth! hail to thee, Thane of
All hail, Macbeth, that shalt be King hereafter! (50-53)
Macbeth is fascinated. The witches give Banquo (Macbeth's best friend) three predictions as well, but while Banquo is curious, he is not really interested in what they have to say.
When the King's messengers greet Macbeth with the news that he is now the Thane of Cawdor (title and lands taken from a traitor), Macbeth begins to believe that the witches were telling him the truth. If he is Cawdor, then he can be king. Quickly he writes home to tell his wife all that has transpired.
Macbeth finally arrives home and his wife, Lady Macbeth, has decided that if she can talk him into being evil and cruel, he will be King and she will be Queen. However, it will take the murder of Duncan, who is Macbeth's King, friend, cousin, and (at the time of the murder) Macbeth's guest.
Macbeth admits that he does not want to kill Duncan, but he does want to be king. He struggles back and forth, ready to change his mind. Lady Macbeth berates her husband. He observes that he really does not need to be king: he has everything.
He does recognize that one thing pushes him on: ambition...his tragic flaw:
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself... (I.vii.25-27)
With Lady Macbeth's encouragement, Macbeth kills Duncan. Macbeth's ambition pushes him to kill Banquo—the only person to witness the witches' predictions—and one who will not lie even for his friend if suspicion falls on Macbeth. Here, then, his ambition takes over. Macbeth also tries to kill Banquo's son Fleance, for the witches said Banquo would father a line of kings. Fleance escapes, and Macbeth worries that the boy will grow up and come back to take the throne. Macbeth feels threatened by Macduff, so he orders Macduff's murder. Macduff is not home—but his family is killed.
In Act Three, Macbeth says he is so "steeped in blood," that he can only continue. With ambition driving him, he becomes a tyrant—finally killed by Macduff, to save Scotland. Macbeth's flaw drives him, and his death is his fault because of his evil choices.