What's the main conflict of Macbeth?

Is it Macbeth's internal struggle or the struggle between the murderous evil represented by Macbeth and Lady Macbeth and the best interests of the nation, represented by Malcolm and Macduff? I'm supposed to say what impact the main conflict has on the play, but I have no idea which of these conflicts my teacher is talking about? Which would you say is the main conflict of the play?