Final answer:
Macbeth is ultimately responsible for his own downfall and destruction due to his ambition and morally questionable choices.
Step-by-step explanation:
In Shakespeare's play Macbeth, there are several factors that contribute to the downfall and destruction of the main character. While all the options presented - Lady Macbeth, the witches, Macbeth himself, and King Duncan - play a role in Macbeth's downfall, the main responsibility ultimately lies with Macbeth himself.
Macbeth is driven by ambition and the thirst for power, which leads him to make a series of morally questionable choices throughout the play. He is easily swayed by the prophecies of the witches and manipulated by Lady Macbeth, but ultimately, it is Macbeth's own actions and decisions that seal his fate.
For example, Macbeth decides to kill King Duncan in order to take the throne, despite his initial doubts and moral qualms. He also orders the murder of Banquo and attempts to kill Macduff's family, showing a willingness to do anything to hold onto power.