In Macbeth, what are some quotes that show Macbeth is not satisfied once he is king?

I would actually want to respond to this question by
looking act Act III scene 1, which is when Macbeth plots the murder of Banquo. At this
stage, he has already gained the crown, but the prophecies of the witches to both
himself and to Banquo still echo in his head and haunt him, and he remembers well that
the witches decreed that Macbeth would not be able to pass down the crown to any
children and that Banquo's heirs would be king. Note what he
says:

To be
thus is nothing, but to be safely thus:

.... He chid the
Sisters,

When first they put the name of King upon
me,

And bade them speak to him; then,
prophet-like,

They hail'd him father to a line of
kings:

Upon my head they plac'd a fruitless
crown,

And put a barren sceptre in my
gripe,

Thence to be wrench'd with an unlineal
hand,

No son of mine
succeeding.

Macbeth clearly
states his dissatisfaction with being King alone in this speech. To be "thus" or to be
King is "nothing" because he fears that he will not be able to hold on to the crown and
pass it on to his descendants. Notice the imagery with which Macbeth describes the
trappings of power that are his because of his position of King. His crown is
"fruitless" and his sceptre is "barren," pointing towards the way that being King is not
enough for Macbeth.