High in Affection and Ambition
Harold Bloom says the Macbeths relationship is the "best marriage in Shakespeare" at the beginning of the play, equal in love and ambition. They are famous for their love: Duncan calls Macbeth's affection "sharp as his spur," while Macbeth calls his wife "dearest partner of greatness" and "dearest love." They are equally close in ambition: her first words include "he that's coming must be provided for," and his letter speaks of "what greatness is promised thee." Duncan's murder is a mutual effort.
Equality Breaks Down
Having characterized their relationship as equal, Shakespeare now breaks down the equality: Macbeth, once crowned, rises in power as his wife descends in importance. All marital affection is lost. She laments that "naught's had, all's spent when our desire is got without content." Meanwhile, he plans the murder of Banquo and, unlike the killing of Duncan, leaves her outside the plot: "Be innocent of the knowledge, dearest chuck." His change from "dearest love" to "dearest chuck" indicates loss of emotional bonding and equality; after their disastrous royal banquet, she calls him "sir."
Fallen to Madness and Death
The marriage's end is characterized as extreme estrangement: they are not only physically separated, but she is steeped in the madness of sleepwalking and hand-washing, while he obsesses over his enemies. Ultimately, the news of her suicide evokes only Macbeth's indifference: "she should have died hereafter, there would have been a time for such a word," a statement that leads to his famous "tomorrow and tomorrow" speech. Their marriage's high affection and ambition has fallen to nihilism and unfelt death-throes.
Relationship as Paradox
Marjorie Garber characterizes the Macbeths' relationship as paradoxical: madly in love, they are childless. Eager for each other's advancement, their mutual ambition destroys them. Partners in crime, they die apart. Once physically separated, they are mentally and emotionally deserted; no fond absence here. Garber and Shakespeare thus seem to agree: the best description for the Macbeths is "fallen to disastrous inequality."