What are some examples of the power of Lady Macbeth in Macbeth?
Right from the start it is clear that Lady Macbeth is the real power behind the throne. She takes on a traditionally male role when constantly pushing, cajoling, and inciting her husband to commit murder:
Glamis thou art, and Cawdor; and shalt be
What thou art promised. Yet do I fear thy nature;
It is too full o' th' milk of human kindness. (act 1, scene 5).
Macbeth is too soft. He needs to discover a backbone if he is to fulfill his destiny and claim the throne. Being gentle is a weakness in a king, and by mentioning this, Lady Macbeth is subtly questioning Macbeth's manhood. She slyly hints that Macbeth is not man enough for the job of killing Duncan. Later on in the scene, Lady Macbeth takes control of the situation. It is now only a matter of time before her husband finally acts:
Only look up clear;
To alter favour ever is to fear:
Leave all the rest to me.
Eventually, Macbeth relents and does as he is bid. However, he still feels incredibly guilty over having carried out the dirty deed. Lady Macbeth, on the other hand, continues to show enormous strength by remaining perfectly calm and rational:
My hands are of your color; but I shame
To wear a heart so white. (act 2, scene 2).
Lady Macbeth is acknowledging her equal role in the murder. She has blood on her hands too. However, unlike her husband, she has no regrets and no remorse for what she has done. The blood seems to have drained out of Macbeth's heart; he is still a weakling despite his murder of Duncan. His wife still has the power, though. Not only would she have gladly carried out the murder herself, she will now plan everything down to the last detail:
That which hath made them drunk hath made me bold;
What hath quench'd them hath given me fire.
It was the owl that shriek'd, the fatal bellman,
Which gives the stern'st good-night. He is about it:
The doors are open; and the surfeited grooms
Do mock their charge with snores: I have drugg'd
That death and nature do contend about them,
Whether they live or die. (act 2, scene 2).
It is telling that Lady Macbeth only gains power through being "unsex'd," that is, defeminized. She has dispensed her female identity to effectively become a man. This raises the question of how much power she really has. In a way, her power is merely a reflection of her husband's own influence. As a woman, she has little or no power. Lady Macbeth realizes that, and that is why she takes on an entirely different gender role in egging her husband on to commit murderous acts.
There is no doubt that Lady Macbeth is power hungry. The mere hint of possibly being queen is enough to spur her toward the nefarious plot of killing King Duncan. I don't think that is the kind of power that you are asking about in your question though. I think that you are referring to power that Lady Macbeth exerts over people. I would say the best examples of that kind of power all occur within Act 1.
. . . and you shall put
This night's great business into my dispatch;
Which shall to all our nights and days to come
Give solely sovereign sway and masterdom.
The above quote occurs soon after Macbeth arrives home in Act 1, Scene 5. Lady Macbeth flat out tells her husband "leave everything to me." You might say that is not an example of power, but when Macbeth responds with more or less "okay," the reader gets the feeling that Macbeth is powerless when compared to his wife.
Later in Act 1, Scene 7, Lady Macbeth once again reasserts her power over Macbeth. Macbeth has decided to not go through with the murder, and Lady Macbeth is not happy about it. She berates and insults Macbeth until he agrees to kill Duncan. My favorite line in that sequence is this:
I have given suck, and know
How tender 'tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this.
Lady Macbeth tells her husband that she would smash a baby if she had agreed to do the deed in order to attain the throne. It's a disgustingly graphic guilt trip toward Macbeth, but it works. Macbeth turns around and murders Duncan.