Why Macbeth kill banquo himself?

Macbeth kills Banquo himself because he considers Banquo a threat to his throne. Banquo is a powerful and ambitious general who has been loyal to Macbeth, but Macbeth knows that Banquo suspects him of murdering King Duncan. Macbeth is afraid that Banquo will eventually try to overthrow him, so he decides to kill him first.

Macbeth also kills Banquo because he is afraid of the witches' prophecy. The witches have told Macbeth that he will become king, but they also say that Banquo's descendants will eventually become kings. Macbeth is determined to make sure that this prophecy does not come true, so he kills Banquo and his son, Fleance.

By killing Banquo, Macbeth removes a potential threat to his throne and ensures that the witches' prophecy will not come true. However, Macbeth's murder of Banquo also leads to his own downfall. Banquo's ghost haunts Macbeth, and he eventually becomes so guilt-ridden that he begins to lose his mind. Macbeth's murder of Banquo is the beginning of his end.