Macbeth's eventual demise is by virtue of his obsession for power and retaining his power. Before he desired the power of being king, Macbeth was a respected noble. He was labeled, "brave Macbeth" (Act I, scene, ii, line 16) for his actions in battle. During a conversation between Duncan and the Captain, the Captain describes how Macbeth brutally slew the rebel Macdonwald:
Disdaining fortune, with his brandished steel,
Which smoked with bloody execution,
... Till he unseamed him from the nave to th' chops,
And fixed his head upon our battlements (act I, scene, ii, lines 17- 23).
In his speech, the Captain describes Macbeth's violence to indicate what a good warrior he is thus showing that he has respect for Macbeth. Once Macbeth became king, he became overpowered with keeping his authority. Macbeth realized that he was being used just so that Banquo's sons can inherit the throne:
They hailed him father to a line of kings.
Upon my head they placed a fruitless crown,
And put a barren sceptre in my gripe,
Thence to be wrenched with an unlineal hand,
No son of mine succeeding (act III, scene 1, lines 60-64).
Macbeth feeling this way convinces a pair of men to kill Banquo and his son Fleance. By having Banquo and Fleance murdered, Macbeth believes that it will prevent Banquo's sons from becoming king. Macbeth also hires the murderers to kill Macduff's family. This demonstrates Macbeth's obsession because...