A person could make a dramatic change of character when they go from a heart of good to a heart of evil. Macbeth is motivated to kill Duncan by Lady Macbeth, but Macbeth is then motivated by fate, and finally motivated by impulse to carry out his next succession of crimes. Macbeth had a hand, or was involved in 3 murders in the story. The first murder was of King Duncan at the beginning of the story with the aid and instructions of Lady Macbeth. The second murder was of Macbeth's best friend Banquo, which Macbeth used the service of three murders to accomplish. It was fate for Macbeth to eliminate Banquo because Banquo was to be the father of kings while Macbeth would not. Finally, the third murder was of Macduff's wife and children. One murderer does the job this time and Macbeth decides from this murder on to act on impulse and not think or feel remorse for any action he does from there on. All these murders indicate that Macbeth doesn't know how to make things right after he has done something wrong, so he does the only thing he thinks is right, and that is to be more violent with each act he commits.
When Macbeth is first introduced, the first impression that we have of him is that he was an incredible and worthy fighter and the King speaks very highly of him. An example of this is "O valiant cousin, worthy gentleman!" The phrase shows that Duncan is very proud of Macbeth, his soldier, and his cousin. In the witches prophecies, Macbeth was told he would be Thane of Glamis, Thane of Cawdor and then eventually become King. He was already Thane of Glamis and he becomes Thane of Cawdor shortly after the execution of the previous Thane, but one prophecy sticks in his mind. He is to become King. Macbeth had the thoughts of becoming King but there was no way he would ever think of murdering his King. He had neither the heart nor determination to do such a violent act. He expresses his discomfort with this in a soliloquy.