Macbeth: Was he a bad person?

Allow me to focus on the titular character of the tragedy MacBeth, by William Shakespeare of Statford-Upon-Avon, and his moral standing and personal character. MacBeth, Thane of Glamis, is a commander in the Scottish army, and the receiver of a prophecy from three Witches: MacBeth is destined to be King. Now, by a medieval view, Kings are divinely chosen, mandated by God. Would this not show the rich character of the man? However, power corrupts. To be chosen to be King, as a man is still on the throne, is a tremendous rush of potential power. The potential for power is a huge driving force, and Macbeth responds with thoughts of killing Duncan. However, bad thoughts don't make bad people (thoughtcrimes, anyone?), bad actions do. Unfortunately, this is a far as my English class has read, so I cannot elaborate upon the actions of MacBeth.