What is a quote that shows that Macbeth is desperate to become king through violence in Macbeth?

Macbeth wants to be king and will overstep anyone to do it.

When Macbeth first gets a visit by three witches, he is just an ordinary solider.  He has recently distinguished himself heroically in battle, but other than that he is a mid-level thane.  The witches put delusions of grandeur into his head, telling him that he will soon be king.  He believes them.

In the meeting with Duncan, the king, Macbeth learns that he is not going to become king the easy way.  Duncan names his son Malcolm heir to the throne, not Macbeth.  When he learns of this, Macbeth becomes angry and lets the audience know in a fiery aside.

The Prince of Cumberland! that is a step
On which I must fall down, or else o'erleap,
For in my way it lies. Stars, hide your fires;
Let not light see my black and deep desires:
The eye wink at the hand; yet let that be,
Which the eye fears, when it is done, to see. (Act 1, Scene 4)

Macbeth does not come right out and say that he is ready to grab a dagger and start doing some damage, but all of that stuff about “deep desires” and the “eye wink at the hand” seems to pretty clearly point to what Macbeth has in mind.  He wants to be king one way or another, and he is willing to kill to get there.

Macbeth writes his wife, and she is all in.  She worries that her husband will not have what it takes to kill to get what he wants.  She is not far off.  Macbeth goes home, and ponders his situation in a soliloquy.

If it were done when 'tis done, then 'twere well
It were done quickly: if the assassination
Could trammel up the consequence, and catch
With his surcease success; that but this blow
Might be the be-all and the end-all here,
But here, upon this bank and shoal of time,
We'ld jump the life to come. (Act 1, Scene 7)

Macbeth is definitely considering violence.  Whereas before he was determined to become king by any means necessary and burning with ambition, this speech demonstrates how he wavers when coming up to the actual act.  Yes, he does want to be king and part of him is willing to do violence to get it.  However, he is also nervous about doing that.

His wife turns out to be the deciding factor.  She is more committed to the plan than he is, and she spurs him on until he finally kills Duncan.  She plots out every aspect of the murder, including framing the attendants and sons, so that Macbeth can become king.