I have to agree with the previous postings. By nature, human are contradictory in their behaviors. As stated, Macbeth is loyal to Duncan at the opening of the play. Unfortunately, with the call of fame and fortune lurking on the horizon, Macbeth loses his loyalty to pursue a darker side of himself.
Macbeth fails to see the importance of being true to ones inner self and finds that he destroys himself in the end.
At the beginning of the play, Macbeth is a loyal subject of King Duncan. He risks his life fighting to protect the kingdom and the king's interests. The king recognizes this and honors him.
At the same time, somewhere in Macbeth's heart is this ambition that will lead him to kill Duncan and become king. This shows how contradictory human nature is since Macbeth can be a loyal vassal and yet have the seeds of treachery within him.
Human nature is often contradictory. Macbeth and Lady Macbeth think they want to be king and queen. They achieve this status through murdering King Duncan.
After their murderous deed, they have guilty feelings. They both have a change of heart, but it is too late. The murderous deed has been committed. They cannot undo what has been done.
If they could undo it, both would. Lady Macbeth tries to wash her hands of bloodstains. She eventually kills herself.
King Macbeth is ultimately beheaded by Macduff. All the power and prestige with being king was not enough to make Macbeth and Lady Macbeth happy. They both die a grievous death and lose the kingdom. Power and prestige gained through murderous deeds did not make Macbeth and Lady Macbeth happy. If anything, it drove them both insane through the hallucinations associated with their murderous deed.