The tragedy of "Othello" lies within the characters themselves. To what extent is this true?

I'd like to comment on at least one character to support
your statement.  Othello's tragedy lies within his own character.  This fact is evident
in Act 3, Scene 3 in which Iago begins his slow manipulation of Othello's perceptions of
Desdemona.  He begins by using one of Othello's strengths to turn him against his wife:
his faith in others.  By hinting that he knows more than he is willing to tell, Iago has
Othello begging him for information about Cassio and Desdemona.  Othello has no reason
not to trust Iago--a man whom he has placed his "absolute trust," a man who has fought
alongside him in battle.

But Othello does not really fall
for Iago's bait completely until Iago makes him question the credibility of Desdemona
falling for someone such as he when Michael Cassio was around.  He calls it "unnatural."
 At this point Othello looks inward,

readability="14">

Haply I am
black

And have not those soft parts of
conversation

That chamberers have, or for I am
declined

Into the vale of years--yet that's not
much-

She's gone, I am abused, and my
relief

Must be to loathe
her.

In this passage, Othello
compares himself to Cassio who has the language of a courtier, is young and white, and
when he does, he finds himself coming out as Cassio's inferior.  So, of course,
Desdemona is in love with Cassio; how could she love him.  It is this conclusion that
makes Othello's fall so heartbreaking and so believable.  Othello falls when he looks at
himself and doubts his own attractiveness to the woman he
loves.

Once Othello decides that he has lost Desdemona, he
moves quickly to have her and Cassio killed.  In his mind, they have committed treason,
and the penalty for such an act is death. He is a soldier, after all, a man of action,
one who must be decisive.  After a brief hearing in Desdemona's bedchambers in which
Othello interrogates Desdemona of her unfaithfulness and further gathering of evidence
that makes the case against her--the ocular proof--Othello moves quickly to execute
her.

Othello's tragedy then stems from his own make-up.  It
is his sense of inferiority when he compares himself to men like Cassio that leads him
to doubt Desdemona's love for him and it's his identity as a soldier that causes him to
trust his ensign over his wife and take decisive action.