The wicked Iago manages to convince Othello that his wife, Desdemona, has been cheating on him with Cassio. It's a complete lie, of course, but Iago's such a skilled manipulator that he's able to play on the Moor's insecurities and convince him of Desdemona's alleged infidelity. Othello reaches such a pitch of jealous rage that he murders his wife, strangling her to death. Othello's own death by suicide is also a result of this tragic misunderstanding.
The death of Iago's wife, Emilia, could also be seen as arising out of a misunderstanding (albeit of a rather different kind). She's always been such a faithful wife to her evil husband, loyally carrying out his wishes and instructions without question. One such example is when she steals the handkerchief from Desdemona which is then used by Iago to frame her for adultery. But when Emilia finally discovers the truth of what Iago's been up to, she bravely confronts him, only to be brutally murdered as a result. Emilia had tragically misunderstood Iago's true nature, and by the time she found out just what he was really like, it was too late.