In both plays there is alot of dramatic irony but also shows revenge and jealousy...
The most obvious subject or theme in Othello is revenge and jealousy. Iago is the main kead to almost everything that happens in these themes. He has been hearing rumours about his wife's affairs with the moor, so he dislikes Othello and must be jealous of Cassio for being lieutenant. However, we can never be completely sure what Iago's motivation is to be so destructive - he manages to get Cassio dismissed but then Iago doesn't seem interested in Cassio's job, only in causing more problems. We also learn that Iago has tried many times in the past to steal the handkerchief that means so much to Othello.