We know that Macbeth meets Aristotles criteria of a tragic hero, because he...

is virtuous - A tragic hero should be a good and noble person of high stature. Their noble characteristics make them compelling while their stature ensures their decisions are far-reaching.
has a tragic flaw - Every tragic hero must have a tragic flaw. In classic literature, this was typically their pride. While pride could be a good thing, excessive pride proves to be fatal to their character.
is tortured - Tragic heroes typically suffer from horrible bad luck or a bad choice, and their handling of that luck leads to suffering. They also suffer and are tortured inwardly by their conscience, leading to a double whammy.
elicits an audience response - Because a tragic hero is a good character, the audience feels the misfortune they suffer. This is called catharsis.