Oedipus is a victim of fate, but he also makes choices that contribute to his downfall. He chooses to disbelieve the oracle's warning and to marry Jocasta, even though he knows that she is the widow of Laius. He chooses to kill the man who crosses his path, even though he does not know who he is. These choices lead to his tragic downfall.
Hamartia
Oedipus' hamartia is his pride and arrogance. He believes that he is invincible and that he can escape his fate. This leads him to make rash decisions that have disastrous consequences.
Catharsis
The audience experiences catharsis when they witness Oedipus' downfall. They feel pity and fear for him, and they are reminded of their own mortality and vulnerability. Oedipus' story teaches us that even the most powerful and seemingly invulnerable people are not immune to tragedy.