Lady Macbeth is depicted as an ambitious, powerful woman, who uses her influence to convince Macbeth to follow through with assassinating King Duncan. After calling upon evil spirits to consume her soul and make her cruel, Lady Macbeth begins to formulate a foolproof plan to murder King Duncan, which she will pitch to her reluctant husband. In act 1, scene 7, Macbeth begins to have second thoughts about committing regicide and decides that he will not follow through with the murder. Lady Macbeth proceeds to criticize his masculinity, call him a coward, and demonstrate her power by telling him,
We fail? But screw your courage to the sticking-place, And we’ll not fail. When Duncan is asleep—Whereto the rather shall his day’s hard journey Soundly invite him—his two chamberlains Will I with wine and wassail so convince That memory, the warder of the brain, Shall be a fume, and the receipt of reason A limbeck only: when in swinish sleep Their drenchèd natures lie as in a death, What cannot you and I perform upon The unguarded Duncan? What not put upon His spongy officers, who shall bear the guilt Of our great quell? (Shakespeare, 1.7.60–73)
Lady Macbeth exercises her authority by successfully convincing her husband to follow her plan and assassinate King Duncan. However, Macbeth is overwhelmed with guilt after committing regicide and refuses to reenter King Duncan's chamber to finish the deed. Lady Macbeth once again demonstrates her authority and resolve by taking matters into her own hands. She proceeds to criticize Macbeth for behaving like a coward and says,
Infirm of purpose! Give me the daggers. The sleeping and the dead Are but as pictures. 'Tis the eye of childhood That fears a painted devil. If he do bleed, I’ll gild the faces of the grooms withal, For it must seem their guilt (Shakespeare, 2.2.51–56).
During Macbeth's feast, he begins to see the Ghost of Banquo, which initially sits down in his seat. Macbeth cannot ignore the ghost, and Lady Macbeth does her best to ease the concerns of the thanes in attendance. After assuring the guests that Macbeth is simply ill, she demonstrates her power by telling him,
O proper stuff! This is the very painting of your fear. This is the air-drawn dagger which you said Led you to Duncan. Oh, these flaws and starts, Impostors to true fear, would well become A woman’s story at a winter’s fire, Authorized by her grandam. Shame itself! Why do you make such faces? When all’s done, You look but on a stool (Shakespeare, 3.4.63–71).
Lady Macbeth's fierce, callous personality and willingness to criticize her husband depict her power and resolute nature. Despite her ambitious, determined personality, Lady Macbeth gradually becomes overwhelmed with guilt and eventually loses her mind.