This is an extremely interesting question to ponder. On the one hand, it cannot be denied that Macbeth, once he starts on his course of bloodletting, becomes ever more murderous and treacherous; and so we can say that his eventual downfall and death are a fitting punishment. Malcolm’s closing assessment of him as a ‘dead butcher’ (V.vi.108) would seem to be quite in keeping with his actions for most of the play.
However, and crucially, Macbeth’s actions are not the only thing that the play chooses to focus on. Even more important, perhaps, is his state of mind, which we the audience are privy to throughout; and we see that, for almost the entire length of the play, he is in a very unhappy state of mind indeed. After much agonising and not a little taunting from his wife, he finally decided to murder Duncan, but immediately before and after this first murder, he is plagued by hallucinations, and upon seeing the blood on his hands he expresses horror and the profoundest regret:
What hands are here! Ha – they pluck out mine eyes!
With all great Neptune’s ocean wash this blood
Clean from my hand? No, this my hand will rather
The multitidunous seas incardine,
Making the green one red. (II.ii.59-63)
Macbeth is already so stricken with remorse that he imagines his bloody hands will stain the entire ocean; it is hard to imagine a more overwhelming sense of guilt than this. And as the play wears on, he becomes ever more desperate and reckless, culminating at last in the famously nihilistic vision which he utters after hearing of the death of his wife.
Life’s but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more. It is a tale
Told by an idiot, full of sound and fury,
Signifying nothing. (V.v.24-28)
Of course, we can say that Macbeth creates hell for himself by his actions, but it is hard not to feel at least a modicum of sympathy when we see how bleak and despairing he becomes.
Furthermore, Macbeth feels greatly beset by outside pressures, the exhortations of his even more ambitious wife, and the prophecies of the three weird sisters. Whether we interpret the witches as being actual external agents of the supernatural predisposing him to his doom, or more just an extension of the inherent evil within himself, it seems that they cannot physically compel him to do anything; but they do serve to inflict, or increase, his mental agonies. Similarly, Lady Macbeth, although she seems much the harder of the two to begin with, succumbs to an even more pronounced mental decline as she begins sleepwalking, scrubbing her hands frantically all the while in a vain bid to assuage her sense of guilt, and finally kills herself.
Macbeth does at least show some spirit in his final battle with Macduff, but nothing like enough to rehabilitate him in any way from point of view of the other characters. For them, Macbeth simply gets his just deserts; his reputation is beyond all salvation. This is not quite the case however with the reader, or audience of the play. Because we see how much he suffers mentally, we are inclined to feel at least a little pity.
Indeed, we might conclude that Macbeth's real punishment is not his death at the end of the play but his own overwhelming inner torment while alive, which, in its intensity, is at least equal to the magnitude of the crimes that he commits.