Why Macbeth kill banquo himself?

Macbeth kills Banquo himself because he considers Banquo to be the biggest threat to his newfound position as king. Banquo is a valiant warrior and a loyal subject of Duncan. He is also the father of Fleance, who, according to the witches' prophecies, is destined to become king. Macbeth fears that Banquo and Fleance will pose a challenge to his kingship and eventually overthrow him.

Therefore, he decides to eliminate Banquo by hiring assassins to kill him. However, the plan fails, and Banquo is only wounded. Angered by the failure of the assassins, Macbeth takes matters into his own hands and personally murders Banquo. He then orders the capture of Fleance, but Fleance manages to escape.

Killing Banquo is a significant turning point in Macbeth's character. It marks the moment when he truly descends into evil and becomes a ruthless tyrant. The act also foreshadows his downfall, as it ensures that the witches' prophecies will eventually come true, leading to his destruction.