The above commentator rightly argues about how Macbeth becomes the king by his ‘foul’ acts. However, it should also be noted that the most important thing Macbeth does in this regard is to prepare himself for the murder of Duncan. And in this case Lady Macbeth’s provocation acts as a supportive force. As the host and his “kinsman” Macbeth first discovers that it would be an unjustifiable act to kill the king. But simultaneously he becomes aware of his “vaulting ambition” which originally forces him to do this ‘foul’ act. Finally Lady Macbeth’s provocation ultimately leads him to perform the action. By that time everyone including the audience has become sure that Macbeth would be “the king hereafter”.
Macbeth's first course of action--suggested and supported by Lady Macbeth--is to kill King Duncan and Duncan's two guards in order to create the opportunity for obtaining the title. When Macbeth becomes aware that Banquo suspects he is the assassin, he arranges to have Banquo and his son Fleance killed as well. Fortunately, Fleance escapes, foiling Macbeth's attempt to subvert the witches' prophecy that Banquo would be the father of kings and solidifying his claim and his potential heirs' claim to the crown. After consulting with the witches a second time, Macbeth decides to have Macduff and his family killed, but to no avail. Macduff joins with Malcolm to defeat Macbeth.