Lady Macbeth is the strongest force of evil. Although her husband is the one who carries out the deed, recall when Macbeth contemplates, “I have no spur to prick the sides of my intent but only vaulting ambition which o’er-leaps itself and falls on the other.” Macbeth would have proved noble just like Hamlet: had certain things gone differently, but Lady Macbeth manipulates Macbeth to the uttermost. When she ridiculed upon his (contrived and untrue) lack of masculinity [after coming back bravely from battle with heaps of honors: go figure.] Lady Macbeth makes the utterly shockingly mind-boggling comment about how she would of dashed out the helpless brain of an infant before she would have forsworn herself: she says Macbeth has proved a sissy [paraphrasingly speaking] in begging to not go through with the assassination of the virtuous King Duncan. Hence forth we get a sense that this women harbors a malevolence and dangerously determined sense of malignant ambition all her own. Lady Macbeth corrupts “the noblest [not Roman] of them all.” Think back to the beginning; when the sergeant lauds Macbeth’s bravery in battle: “Brave Macbeth; well he deserves that name.” Macbeth was doing great; Macbeth was doing wonderfully, but two things went awry: meeting the “weird sisters” and writing his prophetic letter to Lady Macbeth which consequently feuled her already gormandized maliciousness. The “weird sisters” were a force of evil as well, but Macbeth had the sense to put regicide into perspective; even after his mind roamed to regal aspirations. “If chance will have me king why chance may crown me without my stir.” He even tells Lady Macbeth he has decided not to go through with the bloody deed e.g. ( “we will proceed no further in this business.” He just wants to enjoy his new title that he rightfully earned and bask in his new honors, but Lady Macbeth is steadfast in her wickedness to pollute his mind with plethoras of perniciousness. Macbeth knows no way to fend off Lady Macbeth’s ridiculing and mockery. She knows how Macbeth’s mind operates “to the ‘T'” and knows exactly which buttons of Macbeth to push. He is helpless to her upbraidings and mockery, and she knows it full well. She is the serpent under Macbeth’s very nose, and once he is bitten there is no antidote.