This married couple seems to represent opposite ends of the personality spectrum both at the beginning and the end of the play. Macbeth first appears as a loyal and brave supporter of his country and king. While he is savage on the battlefield, he is less capable of conceiving the murder of his cousin and king and is stricken with fear and guilt after he does so. On the contrary, Lady Macbeth is first presented as vicious, conniving and manipulative. She browbeats her husband into committing the murders and feels little guilt or shame immediately after the crime.
After the murder, things begin to change a bit. Macbeth becomes more and more ruthless while his wife begins to feel the effects of repressed guilt. He loses his ability to fear or even feel, even after her suicide. As indicated, her guilt leads her to end her own life, after a bout with sleepwalking and quiet confession.
It is almost as if Lady Macbeth and Macbeth switch positions entirely from the beginning of the play to the end.