Who steps in as the "foil" to Macbeth when Banquo is murdered?
foil: is a minor charater whose attuitudes, beliefs and behavior differ significantly from those of the main charatcer. The foil serves two main purposes:1 to highlight flas in the main character's personality, and 2 to suggest what the main character might have been like if these flaws had not been present. Basnquo, Macebeth's comrade in arms, serves as a foil to Macbeth in the first 3 acts.
Macduff is the logical choice as Macbeth's foil after Banquo is murdered. Macduff is an honorable man, apparently suspicious of Macbeth from the time that the guards are killed. He refuses to attend Macbeth's coronation and thus risks the wrath of the new king. Then Macduff travels secretly to England to meet with Malcolm, who is the rightful king as Prince of Cumberland, and convince him to return to Scotland and overthrow Macbeth. Macduff is not motivated by personal greed; he is concerned about his country.
In everything he does, Macduff shows himself to be a man who acts courageously and honorably. He regrets not telling his wife he was going to Scotland, but he did not expect the tyrant Macbeth to slaughter his family in retaliation. Macduff points out that Macbeth has no children; otherwise, he could not have ordered such a mass murder.
As Macbeth's character deteriorates in the last two acts of the play, Macduff grows stronger and stronger until finally the two men face each other in battle. How fitting that only Macduff, a "man not born of woman," can kill Macbeth.