A prominent theme in Macbeth is the negative consequences of unchecked ambition. Macbeth begins as a man of great potential and stature, only to be ruined by his relentless quest to be the King of Scotland. Because Macbeth has such a great yearning for power, a small trigger by the witches' prophecies clouds his better judgement and ultimately makes him commit atrocities. To make matters worse, after the witches have planted the seed of hope in his mind, Lady Macbeth gives Macbeth the final push that is needed. Whenever Macbeth has a speck of remorse for his actions, Lady Macbeth either challenges his masculinity, or simply reassures his doubts and makes Macbeth shrug off the guilt. She challenges Macbeth's masculinity when Macbeth is reconsidering whether he should carry out the murder of the king:
What beast was't, then,
That made you break this enterprise to me?
When you durst do it, then you were a man;
And, to be more than what you were, you would
Be so much more the man. (I.vii.53-56)
And afterwards, when Macbeth is ranting fearfully after murdering King Duncan, Lady Macbeth calms him by saying comforting words such as, "consider it not so deeply" (II.ii.41). Most notably, Lady Macbeth dismisses the magnitude of Macbeth's murder of Duncan by telling him to wash the "filthy witness from [his] hand," (II.ii.61) implying that his actions can be easily cleansed and erased by simple water. Lady Macbeth is always alongside Macbeth to provide the emotional soothing Macbeth needs, until the very end, when Lady Macbeth herself falls victim to the emotional trauma caused by the terrible crimes the two have committed.
Macbeth's conquest for power brings about many negative consequences. He foremost lies to his dearest, best friend Banquo (eventually killing him too), breaking the bond of brotherhood and trust between them. The first sign of the collapse of this friendship is when Banquo refers to the witches' incident and Macbeth shrugs the topic off like it is trifling business:
I think not of them:
Yet, when we can entreat an hour to serve,
We would spend it in some words upon that business,
If you would grant the time. (II.i.25-28)
Macbeth lies through is teeth to his best friend, indicating the drastic change from being a proper, noble hero, to a deceitful man full of paranoia.
Macbeth also loses the popularity from his other peers. Once a popular warrior famed for his valor on the battlefield and loyalty to the king, Macbeth slowly loses the support from his Scottish noblemen peers Lennox, Macduff, and Ross. His erratic behaviour, such as his guilty outbursts during the feast, combined with poor decisions on his part create the tension between Macbeth and the Scottish noblemen. For example, the murdering of Macduff's family only serves to incite Macduff and cause him to become more determined to exact revenge on Macbeth. Macbeth's ambition formulates a despicable character that negatively affects his popularity. Because of this, eventually, none of the Scottish noblemen that were once loyal to Macbeth choose to side with him in the final siege and Macbeth is left to be doomed by himself.
As Macbeth is consumed by his ambition to become king, he loses his moral values. He changes from a virtuous man to one who constantly uses violence as the solution to his problems (as seen with Banquo, Fleance, and Macduff). Macbeth also has no regard for his country anymore: once he takes the throne, he leaves his country in a state of complete shambles. Macbeth becomes king to satisfy his own greed, rather than to serve his country and demonstrate his leadership. Macbeth’s unrelenting ambition transforms him into someone without a moral code, who obtains his objectives with no regard to the means used and the consequences.
Macbeth’s betrayal of his closest friend, his loss of support from his circle of peers, loss of moral values, and his rash decisions all ultimately contribute to his tragic downfall. Macbeth’s downfall demonstrates how misguided and uncontrolled ambition can be deleterious.