With Shakespeare's Macbeth being a "tragedy of the imagination," as renowned critic Harold Bloom claims, the most tragic death is that of Macbeth himself as his demise provides him an understanding of himself and arouses the most pity in the audience who, to some extent identify with his imagination. Like Macbeth, the audience, too, conscious of an ambition or desire, often perceive themselves as having already committed the deed that will take them to the future where the act is a fait accompli [something that already has been accomplished]. Indeed, it is this similar condition of people's own imaginations that arouses the fear in the audience about Macbeth's tragedy of imagination.
Following the definition of the tragic hero as set forth by Aristotle in his Poetics, then, in addition to Macbeth's arousing pathos and ethos in his audience, he also suffers a misfortune that is not entirely his own fault. Under the influence of the preternatural world of the three witches and goaded by his beloved wife, who challenges his very masculinity, Macbeth commits the murder of Duncan, a murder he has not desired.
Also adhering to Aristotle's definition of the tragic hero, unlike Lady Macbeth who dies in madness, Macbeth, before his death, gains self-knowledge. For, as Macduff, "not of woman born" defeats him, Macbeth realizes that he has been a victim of his own his "proleptic imagination," [Bloom], an imagination that takes him to the deed completed before it has really happened.