A potential thesis statement:
Both Othello and Oedipus embody the tragic flaw of rash and headstrong emotion-driven action; however Othello is motivated by intense love and jealousy (which leads to his murder of Desdemona), while Oedipus is motivated by pride and intense anger (which leads to the murder of his true father, Laius).
In this essay, you would need to show examples of how the tragic flaw of emotional extremity obscures the better judgement of each and eventually brings his downfall. Make sure to show ways that they are similar and ways that they differ from one another.
You will also need to make sure to compare and contrast the effects of pride and anger on Oedipus' circumstances with the effects of extreme love and jealousy on Othello's. Again, point out specific similarities and specific differences.
I can suggest you a thesis statement regarding the compare-contrast issue between the murders done by Othello and Oedipus. This is as follows:
Both Shakespeare's Othello and Sophocles's Oedipus Rex kill their kin out of pride, though, Othello murders Desdemona being influenced by others, while Oedipus's killing his father Laius is driven mostly by his freewill and partly by his fate.
In the statement, the titles along with the key phrases are included. Yet, another suggestion is:
Both the murders performed by Othello in Shakespeare's Othello and Oedipus in Sophocles's Oedipus Rex are quite similar in terms of their motives; but they are completely contrasting in terms of all the influential phenomena which drive the heroes to perform the act of murder, especially regarding the issue of fate versus freewill.
Now, you can choose either if you like.