Final answer:
Macbeth's moral character has changed from a noble warrior to a treacherous tyrant since the witches' prophecy. Driven by ambition and manipulated by Lady Macbeth, he descends into guilt and paranoia, marked by a series of increasingly ruthless actions to maintain power.
Step-by-step explanation:
Since his first encounter with the weird sisters in Act 1 Scene 3 of Macbeth, Macbeth's moral character has deteriorated significantly. Initially, Macbeth is presented as a valiant and honorable warrior. However, after the witches prophesy that he will become Thane of Cawdor and eventually the King of Scotland, his curiosity and ambition are sparked.
Upon learning that the prophecy about becoming the Thane of Cawdor has come true, Macbeth begins to harbor thoughts of murdering King Duncan to fulfill the remainder of the prophecy. His morality is further compromised under the influence of Lady Macbeth, who questions his manhood and bravery, manipulating him into committing regicide. Macbeth's transformation is driven by his growing ambition and susceptibility to manipulation, leading him from a noble thane to a treacherous tyrant who is haunted by guilt and paranoia.
As the play progresses, Macbeth's actions become increasingly ruthless, paranoid, and devoid of the honor that once defined him. The murder of Duncan marks the turning point in his moral decline, and he continues to commit more atrocities to maintain his power, demonstrating the profound and tragic change in his character since the witches' foretelling.