What is the tragedy in "Macbeth"?

Macbeth is a tragedy because a relatively good man who has the qualities to become a great man is derailed by his greed and lust for power.The prophecies of the witches begin his journey down the path of destruction. He could have ignored them, as Banquo did, and allowed fate take its course. Instead, with the encouragement of his wife, he takes matters into his own hands, murders his king and from then on his ambition overtakes him. He lets nothing or no one get in the way of his success.He has chances to reverse his course, but his ambition is too strong. By the time the play is over, his wife has gone mad and killed herself, Macbeth has had Banquo killed, along with his wife and young son, and Scotland is in disarray. Believing his will not be killed by "a man born of a woman" he is killed nevertheless by a man born by Caesarian section. He has lost everything, including his kingdom and his reputation.