In Macbeth, in Act III, Scene II, how does Macbeth show his resolve and ambition have become stronger?

This is an immensely revealing scene that shows the spiral
of corruption and evil that Macbeth has entered into and how he is descending rapidly
downwards towards ever greater moral degradation. What is key to note about this scene
is the way in which Macbeth and Lady Macbeth have, in some ways, exchanged places. Now
it is Macbeth who is plotting to kill Banquo and Fleance by himself, whereas before he
needed her assistance and encouragement. He even goes as far as to not involve her in
any way, telling her, politely, to mind her own
business:

Be
innocent of the knowledge, dearest chuck,

Till thou applaud
the deed.

This shows the
extent to which Macbeth has embraced evil. In addition, just after saying this, Macbeth
makes an imprecatory speech to night, in much the same way that Lady Macbeth abandoned
herself to the forces of evil in Act I scene 5. Note his
words:

Come,
seeling Night,

Scarf up the tender eye of pitiful
Day,

And, with thy bloody and invisible
hand,

Cancel and tear to pieces that great
bond

Which keeps me
pale!

This clearly represents
an attempt by Macbeth to fill his whole body with darkness and evil. We see a greatly
changed Macbeth. He now needs no Lady Macbeth to cajole and shame him into action. He
has embraced evil, and shows clearly how one bad act leads to ever greater
transgression.