What is hideous in Othello?

In Othello, there is grotesque
sexual and animalistic imagery, which is quite hideous.
 Iago says to Brabantio, regarding Othello and Desdemona's
relationship:

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I am one, sir, that comes to tell you
your daughter
and the Moor are now making the beast with
two
backs.

Jealousy
is personified as both hideous and a monster.  Iago warns
Othello:

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O, beware, my lord, of
jealousy;
It is the green-eyed monster which doth
mock
The meat it feeds
on;

Cassio says
that if a man loses his reputation he becomes hideous and
bestial:

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Reputation, reputation, reputation! O, I
have lost
my reputation! I have lost the immortal part
of
myself, and what remains is bestial. My
reputation,
Iago, my
reputation!

Emilia
uses hideous gastro-intestinal imagery to describe the way men treat
women:

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They are all but stomachs, and we all
but food;
To eat us hungerly, and when they are
full,
They belch
us.

The
word "hideous" is only used once in the play, used by Othello to refer to a monster that
could mean both himself or Iago.  It could also stand for jealousy (Othello) or deceit
(Iago) personified.

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By heaven, he echoes
me,
As if there were some monster in his
thought
Too hideous to be
shown.

All in all,
Iago is the most hideous character in the play.  He is a sexist misogynist, the devil
incarnate, an agent of chaos and destruction.  He seems to revel in pain, even his own.
 And he wonderfully uses language as his primary weapon.  When he is stabbed and all his
injuries inflicted, he goes silent.