Power
Don Barth
"My voice is in my sword, thou bloodier villain than terms can give thee out!"
This shows Macbeth's power because all of the power of being king gets to his head and he wants to fight Macduff.
"I go, and it's done: the bell invites me. Hear it not, Duncan, for it is a kneel that summons thee to heaven or to hell."
Macbeth kills the King Duncan. This shows power because he killed the king so he can become king for himself.
"We have scotch'd the snake, not kill'd it."
Macbeth is saying the he still needs to kill Banquo, and him killing Banquo shows his power.
Evaluation of Shakespeare
Shakespeare is saying that too much power can be a good thing and a bad thing. He uses this effectively because when Shakespeare uses the example of power, you can expect something bad to happen.