Macbeth is initially seen as a great soldier, a fearless fighter who has loyally defended his king against a treacherous rebellion, however his own actions proved him and others that he wasn’t as wonderful as people first thought. Macbeth’s actions lead to his own downfall because it was him that murdered Duncan and his choice to get assassins to kill his best friend Banquo and Macduff's innocent wife and children. "Not in the legions of horrid hell can move a devil more damned in evils to top Macbeth" (Act 4, Scene 3) Macduff says when he found out Macbeth had his family assassinated. Macbeth didn’t have to turn to crime to fulfil his greed. He does know right from wrong. He does have a conscience, but it does not guide his actions.
All of the problems start when Macbeth killed Duncan. He commits the murder because he is way too ambitious and weak willed for his own good. If he wasn’t so determined to be king, then he would never had killed Duncan, Banquo, or Macduff's family. The Witches predicted that Macbeth would be crowned king, this fed his ambition to become king and prompted him to murder Duncan. "Screw your courage to the sticking place and we'll not fail" (Act 1, Scene7) Lady Macbeth taunts her morally weak husband to go through with her plan of killing the king. Her persuasion mixed with the three Witches prophecies eventually gets to the weak-minded Macbeth.
Jealousy, selfishness