There are several elements of reversal, or changes, in Act 2 of Macbeth. First of all, Macbeth was a loyal subject in Act 1, but he is king now. Lady Macbeth was his cheerleader and the one pushing him on, but she is now completely in the dark. Finally, Banquo was Macbeth’s friend and confidant in Act 1, but now in Act 2 he is suspicious of him enough to kill him in Act 3.
First of all, Macbeth has reversed from loyal subject to murderer. This is a reversal in itself, because in Act 1 Macbeth did not want to kill Duncan. When he imagines the bloody dagger, he talks to it as if it exists to convince him.
Thou marshall'st me the way that I was going,(50)
And such an instrument I was to use.
Mine eyes are made the fools o’ the other senses,
Or else worth all the rest. (Act 2, Scene 1, p. 27)
Thus with the appearance of the dagger Macbeth reverses again, from not wanting to kill Duncan to killing him. He changes from loyal subject to murderer.
Another change in Act 2 is that Lady Macbeth is no longer in charge. In Act 1 she made all the plans, but now she is completely out of the loop. Macbeth does not tell her what he is doing in regards to Banquo or Macduff. By Act 3, Scene 2, she has no idea what is going on.
What's to be done?
Be innocent of the knowledge, dearest chuck,(50)
Till thou applaud the deed. (Act 3, Scene 2, 46)
Since she is still directing him in the beginning Act 2 for Duncan’s murder, there clearly is a reversal of power here.
Finally, Banquo and Macbeth are good friends in the beginning. They both see the prophecy together, and the prophecy concerns both of them. Yet by Act 2, Macbeth is pulling away from Banquo. Banquo is suspicious of Macbeth.
Thou hast it now: King, Cawdor, Glamis, all,
As the weird women promised, and I fear
Thou play'dst most foully for't: (Act 2, Scene 1, p. 40)
Macbeth is aware that Banquo is suspicious, and tries to play casual. Macbeth calls Banquo “chief guest” but at the same time is plotting to kill him.