I think that Othello is undone by words more so than the sword. From the most fundamental point of view, he is undone by emotions, which are even more primary than words. The self- doubt and insecurity that is triggered by Iago's words represents something even more primal and instinctual to all human beings. Othello's self- hatred and disbelief that he could be entitled to a woman such as Desdemona is what enables him to believe the words of Iago. He is weak at his very core. It is here that Shakespeare might be attempting to reveal some element of human nature. In the end, it is not words or weapons that snuff out the life of human beings and the potential hope for redemption in consciousness. Rather, it is within our own sense of self where disaster lies. Certainly, this is true in the case of Othello, and something that is brought out in both his rise and fall. There is a very primal hollowness within the individual that reflects a basic nature of human beings. In this, Othello is undone by himself, and not as much by the words of others or of weapons. In this, the internal, not the external, is both the source of the human's greatest strength and simultaneously their most pathetic of weaknesses.
Othello is undone by words because he allows himself to be manipulated by Iago's lies. Iago secretly hates Othello and uses Othello's extreme jealousy to benefit himself. He leads Othello to believe that Desdemona has been unfaithful to him. Although Othello loves Desdemona, he kills her because he thinks she has betrayed him. When Iago's lies are finally exposed, Othello is overcome with grief. Othello learns he will be forced to stand trial for his actions. However, he commits suicide because he cannot live with what he has done. Othello's downfall is a result of his misplaced trust in Iago's false words.