What is Othello’s flaw and how does he grapple with it?

Like all great tragic heroes, Othello is flawed.  Iago
finds this flaw and exploits it.  His flaw is his insecurity in his marriage and Iago
awakens his jealousy and uses it to destroy him and
others.

Since Othello is black and Desdemona is white, her
father believes that Othello enchanted her.  It is the only explanation he can
accept.

In Act I, scene 3, Othello tells the Duke his
story.  One could say that indeed Othello enchanted Desdemona but not in a negative
sense.  His personal story was one of adventure and exotic people and places.  He had
been a slave and was now a great general.  Desdemona seemed to hang on his every word
and as a result, fell in love with him.

Living the life he
had lived deprived him of love and affection.  As a result, Iago could exploit this
insecurity and arouse his jealousy, aka the green eyed monster.