It is difficult to say that it is Macbeth's determination that makes him a bad person. He is more characterized by ambition, and an excessive faith in the witches, which drive him to carry out some very evil deeds. Macbeth does not really show determination to kill Duncan--indeed he is chastised by his wife in Act I, Scene 7 when he briefly decides to put off the murder. Early in the play, it is Lady Macbeth who shows determination, pushing Macbeth to murder the king and later encouraging him to put his qualms about murdering Banquo aside. Later in the play, though, Macbeth is completely determined to do whatever is necessary to maintain his power, including the murder of Macduff's family, but one might say that he had little choice by that point but to stick it out to the bitter end at that point. Having gained the crown by murder, there was no way to keep it except through further violence and murder. Yet even in the final scene, when it is revealed that he has been fooled by the witches' prophecy, he briefly refuses to fight Macduff, only doing so when he realizes that his only other option is humiliation and death.