In Othello, there are many instances of jealousy. Three that come to mind which would easily divide into paragraphs include these:
1. Iago's jealousy of Cassio - This jealousy occured in the first act, yet is carried out throughout the play. Cassio earned a promotion that Iago had hoped to receive. This motivates a great majority of Iago's actions and it results in many deaths.
2. Othello's jealousy of Cassio - Othello allows Iago to convince him that Desdemona is having some kind of relationship with Cassio. After many staged instances, Othello acts on this jealousy and eventually murders as a result of believing Iago's lies.
3. Roderigo's jealousy of Cassio - Roderigo maintains a position as a secondary character throughout the text, but he allows his motivation to become a suitor to Desdemona to get the better of him. Iago convinces him that there is something between Cassio and Desdemona and this helps Roderigo attempt to kill Cassio by the end.
All of these jealousies spring from the effort of Iago. All of these jealousies take their ultimate fall on the character of Cassio. Each instance of jealousy actually loses each character what they really had wanted.