Based on the theme of the play, Macbeth and Macduff are each both good and evil. For examples, Macbeth is good because he feels guilt. Macduff is evil because he kills Macbeth.
Tragedy is impossible if Macbeth or any hero is wholly good - or wholly - evil. The journey downward of Macbeth to murder and madness makes for such gripping drama in that at every stage of this journey, Macbeth is able to stop, step back, and return to his path as the heroic leader of men that we find him at the play's beginning. The Weyward Sisters prophecies of future greatness do not force Macbeth to kill. Not even when he hears Duncan choose Malcolm as heir to the throne does Macbeth need to act. There is no imperative aside from his and Lady Macbeth's vaultig ambition that he become king. Again, we are introduced to him as a loyal thane of the realm and supporter of the crown. He does not need to give in to the prophecy to be great, great and valorous he is already -- and so acknowledged by his own king.
Macbeth and Lady Macbeth are initially so close to each other and loving that they almost complete each other's sentences. That is until the morning after the murder of Duncan when Macbeth, who proves either to have more conscience -- or less guts -- than his wife, begins to pull away.