In Macbeth, Macbeth's tragic flaw is his lust for power. To arrive at this answer, one can analyze Macbeth's actions and character throughout the play. Macbeth's desire for power drives him to eliminate anyone who stands in his way, including his friend Banquo and the innocent Macduff family. His ambition consumes him, leading to his downfall and the tragic events of the play. Additionally, Macbeth's soliloquies and conversations with Lady Macbeth reveal his constant obsession with gaining and maintaining power, which ultimately leads to his demise.
