VII.34) Lady Macbeth is there to set him straight, accusing him of "living a coward" (I.VII.47). She gives off an aura of ruthless confidence, never straying from her ultimate goal and willing to do whatever it takes to finish the job. Due to this, Macbeth accuses her of being masculine, wishing that she "bring forth men-children only" (I.VII.82). Despite the negative connotations of Macbeth's remarks, Lady Macbeth accepts this role and is able to convince Macbeth to the point where he is "settled and bend up commit every corporal agent to this terrible feat" (I.VII.91-92). Where Macbeth is weak, Lady Macbeth is strong, allowing the crown to be bestowed upon Macbeth's head.
After having killed Duncan and having ascended to the throne, Macbeth recounts his encounter with the witches where he was told of the destiny of Banquo's children. Upon remembering this encounter, Macbeth worries that "for Banquo's issue have I [Macbeth] filed my mind" (III.I.70). From here Macbeth forms his plan to kill the noble Banquo, yet he refuses to directly inform Lady Macbeth of his plan. Lady Macbeth tells him that he "must leave this" (III.II.40), but Macbeth disregards her comments, as he is dead set on killing Banquo. Macbeth asks Lady Macbeth to "be innocent of the knowledge" (III.II.51) concerning Banquo's killing. He notices that Lady Macbeth has figured out his plan, saying she "marvel'st at my [Macbeth's] words" (III.II.61). Having discerned that Macbeth intends to slay the innocent Banquo, Lady Macbeth is shocked as she can not fathom that this is the same Macbeth who could barely kill King Duncan. She begins realizing the impact that she had on Macbeth by convincing him to kill Duncan and she sees how darkly his character has changed.
Although Macbeth's murderous actions show how he has been corrupted by his hunger for power, he is still overtaken with great guilt over killing Banquo as exemplified by Macbeth's visions of Banquo's ghost.