How did Macbeth's character change?

When we first meet Macbeth, he is a general in the king's army and originally the Thane of Glamis. Valiant and loyal, Macbeth is also named the Thane of Cawdor. Macbeth is not evil at heart, but his ambition, made evermore evident by his wife's determination and enthusiasm, leads him to commits regicide and eventually orders the death of women and children alike. Macbeth's initial crime is a product of opportunistic prophecies. In hearing the prophecies, Macbeth's weakness is unveiled, and his "vaulting ambition," in addition to his wife's influence, moves the plot and transforms the man. Thereafter, Macbeth's decision compels him to commit further crimes in an attempt to cover his tracks and defy the three witches' prophecy.