Was it necessary for the characters in Macbeth to do such terrifying acts?

As a morality tale of sorts, Macbeth has as its near contemporary Christopher Marlowe’s Dr. Faustus. Like Dr. Faustus, Macbeth recognizes the damning consequences of his crime:

. . . Besides, this Duncan
Hath borne his faculties so meek, hath been
So clear in his great office, that his virtues
Will plead like angels, trumpet-tongued against
The deep damnation of his taking-off.” (I vii 16-20)

And yet Macbeth carries out the crime, thus precipitating his own descent into hell. Later in the play, appropriately, Macduff calls Macbeth by the name of “hell-hound” (V x 3). Indeed, the story of Macbeth is that of a man who acquiesces in his damnation—in part because he cannot utter words that may attenuate his crime. As Duncan’s guards pray “God bless us” on their deathbed, Macbeth cannot say one “Amen” (II ii 26-27). His fate is thus sealed entirely by his own hands.