One common theme in Animal Farm and Macbeth is that men/pigs will desire power above all else. Macbeth becomes so obsessed with power that he consigns himself to kill anyone who poses as a threat to his reign. Napoleon similarly changes the rules on the barn to keep the other animals oppressed enough to allow him to continue.
Just using Napoleon and Macbeth as examples of conflict:
Externally, Macbeth is influenced by the suggestive ambitions of his wife and reacts with reckless violence to the visions of the witches. Internally, he is conflicted throughout the play: his own ambition for power and his fear of losing it and the increasing guilt, most notable in his hallucination of Banquo, which becomes a kind of internal and external influence.
Napoleon, on the other hand, does not seem conflicted at all. Initially, he, like the other animals, is oppressed by Farmer Jones to the point where they take up the revolution. Once he gains all power and ousts Snowball (comparable to Macbeth’s killing of Banqo), he does not seem to be internally or externally conflicted. Napoleon does everything to maintain his power and this includes making enemies or friends; as he does with Frederick and Pilkington.