Lady Macbeth, who perhaps knows him best, says: "Thou art not without ambition, But without the illness should attend it."
Macbeth is empowered by consuming ambition, but he is an essentially good character. That is why after hearing the witches' prophecy he assures himself that "Chance may crown me without my stir." He is indecisive, and would not have killed Duncan without the ambitious Lady Macbeth's steely sense of purpose that is the driving force behind Macbeth, who is weak enough to be manipulated by her. When in Act I, sc vii, Macbeth decides not to kill Duncan, his wife knows exactly how to invoke his desire for kingship by questioning his manhood. Nevertheless, the two are very close and Macbeth hides nothing from his "dearest partner of greatness."
Macbeth comes across as an emotional easily excitable character. His letter to Lady Macbeth shows an unconcealed, almost childish excitement at the prospect of becoming king. His mood swings are sudden and frequent, with a sudden high when he hears the prophecy, then plummeting down when Malcolm is named as the next king.
After the murder of Duncan, Macbeth is horrified and his dying goodness causes him to awaken to a guilt that will remain with him until his death. We see his desperation when he overreacts when Duncan's corpse is discovered.
The months after Macbeth's crowning prove him to be a pathetic king. Everything that we hear tells us that Macbeth has become a cruel tyrant and changed Scotland into a country 'almost afraid to know itself.' He trusts no one and sets spies on each of the thanes. He will not even trust the witches, and is determined to make "assurance double sure" by slaughtering Macduff's entire family for no reason. Indeed "the robes of kingship" have proved to be far too big for him.
Macbeth is now a man so desperate that he must act without considering the reasons for acting ("Strange things I have in head…scanned"). Macbeth finally seems to realize the enormity of his sin, yet he knows that if he thinks about it he will surely go mad. Thus the new Macbeth confronts the witches and their answers first give him confidence, then alarm as despite all reassurances, the witches still predict Banquo's heirs as future kings. It is here that Macbeth's desperate confidence begins to falter (he curses the witches). He desperately tries to reassure himself with the witches' prophecies but inside he knows that he is defeated. He is cynically wise, regretful that he will have none of the things that old age needs: neither friends, nor respect, nor love, nor support. As he waits for the approaching army to overpower his castle, he is a man totally destroyed. Seyton tells him that his wife is dead, but he cannot even grieve for the woman who was once his 'dearest partner'; life simply has no meaning.
Macbeth chooses to die in battle, 'with harness on our back', and this decision perhaps revives a spark of our former respect for the mighty warrior. He is killed, as he knew he would be, at the hands of Macduff. In the closing speech of the play, the newly crowned Malcolm calls him a 'dead butcher', but we know that he was more than that. Macbeth was not irrevocably evil. He was, rather, a normal man who succumbed to his greed and lust for power, and chose to do something evil. That is what makes Macbeth a tragic hero and the play a tragedy.
