Macbeth's tragic flaw, as revealed in act 1, is Ambition. He is so ambitious that he will stop at nothing to achieve his goals, which is seen later during the play.
Macbeth's tragic flaw is his desire to be the King. He's ambition for power and position influenced him. That is why, he is will to give up everything just to get that desire. All of his ambitions are the reasons for his downfall.
