Just like it says at the top, folks. This is a chunk out of a paper I wrote in college. I never titled anything. I wrote these papers with the wildest of abandon. Let's power through.
MacDuff's status as archetypal hero is most demonstrable at the point when Macbeth has MacDuff's wife and children. It is an action like this, which almost always precedes the hero's 'dark night of the soul' or 'moment of doubt'. MacDuff could have, until this point, walked away. Macbeth had in no way directly wronged him. He could have not done anything, but the slaughter of his family thrusts him headlong into his role as the hero.
Basically, my theory was that Macbeth was not a tragic figure, but the natural progression and end of an archetypal villain. Top that!