In Macbeth Act 4 scene 3, quote the lines in which Macduff swears personal vengeance on Macbeth.

What is interesting about the way that Macduff swears
vengeance upon Macbeth in my mind is the role of Malcolm in manipulating him towards
expressing his vow of revenge. Note the way that, at first, after he has heard the
terrible news. Macduff is shocked and repeatedly asks if all of his children were
killed. At first, he berates himself for their deaths, because he deserted them.
However, note what Malcolm says to him to bring him out of his grief and to move him
towards thoughts of murderous vengeance:

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Be this the whetstone of your sword: let
grief

Convert to anger; blunt not the heart, enrage
it.

Note Malcolm's role in
encouraging Macduff to use his grief to spur on his desire for bloody vengeance, which
Macduff does in lines 232-234:

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Bring thou this fiend of Scotland, and
myself;

Within my sword's length set him; if he
'scape,

Heaven forgive him
too!

Thus it is that Macduff
sets himself up against Macbeth as his nemesis, which prepares us for the drama of the
final act.