Consider the power of a lie. Oedipus grew up thinking he was someone else's son and the truth unfurled destiny. Othello was happy in his marriage until he was plagued by the lies and schemes of Iago. How much of a role did fate play in the fault of men? Argue whether in those plays it is men's will and their words which will shape the tragic hero's destiny, the hand of fate, or both. Take into account Aristotle's definition of what makes a tragic hero.

Aristotle defined the tragic hero as one whose error in judgment leads to his downfall. While fate plays the major role in Oedipus's downfall, both Oedipus and Othello make mistakes due to a tragic flaw in themselves that leads to errors in judgment.
Oedipus is destined to murder his mother and marry his mother. That is his inescapable fate, and why initially, he is meant to be killed as an infant. He doesn't know this fate, because people have lied to him about his real identity. On some fundamental level, the lies don't matter--his fate is going to be the same regardless of what people say to him. And the lies are well meant, part of a hope he can defy his destiny.  
Although his fate is preordained, his own flaw, his hubris or pride, makes the situation worse. He simply can't imagine that he might be the cause of the plague in Thebes. Had he had less pride, the truth might have been easier for him to bear; the consequences less dire. He might, for example, have been able to truly see with his inner eyes without having had to blind himself.
In Othello, there is no sense that Othello's fate is preordained. No gods or oracles have  decreed he will murder his wife. In this case,  therefore, Iago's lies and Othello's own tragic flaws loom larger in the tragedy that unfolds.
Othello's flaw is his insecurity. For all his success as a military leader, he can't truly believe that Desdemona could love him. His error in judgment is in trusting Iago. Iago's lies are not well-meant. Iago wants to destroy him. If Othello had had more confidence in his ability to be loved by a woman and more ability to discern Iago's falseness, this tragedy could have been averted.