How does Macbeth define the meaning of pure evil and its vision? (Vision of pure evil.)

In Act 1 a wounded captain has come out of the battle to
tell King Duncan about the manner in which Macbeth has destroyed the merciless
Macdonwald. The passage is perhaps the most violent in all of
Shakespeare.

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Till he unseamed him from the nave to th’
chaps

And fixed his head upon our battlements.
(!.ii.20-21)

Later, one of
the nobles is explaining to King Duncan about another tremendous victory of Macbeth and
Banquo’s in which Macbeth is described as Bellona’s bridegroom. Because Bellona is the
goddess of war, this means that Macbeth is being called the god Mars himself, a great
killing machine. It is this extraordinary personage, a man of ordinary intellect but a
fantastic power of imagination that has a tremendous potential and skill for killing.
Shakespeare sets Macbeth up as a killer from the very beginning of the
play.