I would say that the main change I see is from a man who, at the beginning of the play, has interest and passion for life and for his wife, to a man who has lost all connection to the aliveness of life. He becomes a killing machine and loses a great part of his humanity, his ability to feel.
In the early scenes, there is a lot of "lustiness" in the way Macbeth argues with his wife, debates his own decisions before the audience and even plots the murder of Banquo to seal his future. But as those who pursue a path of pure evil or "selling of one's soul to the devil," are often warned, the killing and distancing of himself from everyone around him, including Lady Macbeth, separates him from his humanity. So that, in Act V, scene v, he cannot even offer more in response to his queen's death than, "She should have died hereafter."
This speech that goes on with "Tomorrow and tomorrow and tomoorw," one of the most famous in all of Shakespeare, denotes the deadness (though he is physically alive) that exists inside Macbeth by the end of the play. He says, in essence, that life is a sham and it contains lots of "sound and fury," but all the pomp and noise of life ultimately signifies "nothing."
Macbeth is a broken man by the end of the play. Some might even argue that he is no longer a man at all, having lost the human ability to feel and value life itself.
In Shakespeare's Macbeth, Macbeth does change during the play. I'll outline some of the changes for you.
- Early in the play, Macbeth takes justice and honor, as well as consequences, under consideration before he is convinced by his wife and his own ambition to assassinate Duncan.
- After killing Duncan, he considers nothing before killing the two innocent grooms. This is also the sign that he is no longer willing to let his wife bully him, as he did before the assassination. Later, he orders the deaths of Macduff's family without a second thought.
- He not only doesn't consider that he is killing a friend and fellow thane when he orders Banquo's death, but he orders the death of Banquo's son, as well--all for the sake of maintaining power and securing his legacy.
- He also suffers from great guilt just before and just after killing Duncan, but he shows little sign of feeling guilty once he kills the grooms. He finds no peace and cannot sleep after he kills Duncan, but that's mostly because he does not feel secure in his power. He fears insurrection.
- In Act 5, Macbeth vacillates, or goes back and forth, between believing he is indestructible (due to the witches' predictions) and knowing the predictions are too good to be true and he is doomed. He suffers despair and slides into nihilism when he receives the news that his wife is dead.
- Still, in the end, he dies a noble death, meeting Macduff face-to-face in battle.