Critics normally group four of Shakespeare's tragedies as his greatest works: Hamlet,  Othello,  Macbeth, and King Lear.  Of these Othello is often considered his most pure tragedy, and by that I suppose we mean that it is unconfused with other emotional responses.  Most sympathetic viewers leaving the theater after a performance of Othello are emotionally drained.  They feel anger, hatred, and contempt for Iago; an odd mixture of sympathy and frustration for Othello; but utter compassion even pity for the beautiful and virtuous Desdemona, who is Shakespeare's most feminine leading woman.  She is neither weak, like Ophelia, headstrong like Cordelia, and certainly not ambitious, like Lady Macbeth.  Desdemona is most men's ideal as the perfect wife: gorgeous and loyal, but compliant and sensuous.  She is, however, among Shakespeare's great heroines, the only one who dies by her husband's hand the victim of a motiveless plot to defame her.

By pure tragedy we may also mean that it is extraordinarily concentrated. The bulk of the action from the beginning of Act II to the end of the play covers barely more than twenty-four hours.  Unlike most of Shakespeare's other plays, there really is no sub-plot, nor is there any political or moral theme.  All of Shakespeare's tragedies have a strong domestic thread running through them, but Othello seems almost exclusively a domestic tragedy.  Even the means of death is stripped of intervening tools.  Othello does not use a dagger, sword, poison, or a rope, rather he kills Desdemona by hand using only a handy pillow for suffocation.

Her death is a waste of life which we feel like no other in all of Shakespeare.  Hamlet brought many of his problems on himself.  Macbeth has so covered himself in blood that he can hardly be called a tragic hero, King Lear is old and befuddled and there is really nothing left for him but death.  Only his daughter, Cordelia, rivals Desdemona as an unjustified slaying.  But we do not know Cordelia as well as Desdemona nor do we actually see her killed on stage as we will see Desdemona.