A hereditary curse placed on his family is the reason for the downfall of Oedipus Rex. He unknowingly fulfills the prophecy of the curse by killing Laius and marrying his mother, Jocasta. One flaw in the character of Oedipus Rex is his pride, or hubris, and his treatment of Creon and Teiresias demonstrate this flaw. However, I don't think that Oedipus Rex can be blamed for any flaw he may have in his character since he isn't directly responsible for it. Can we blame Laius and Jocasta for not raising him themselves so they could attempt to prevent the prophecy? Perhaps Jocasta herself is more blameworthy as she tries to keep the truth from Oedipus and the others. Can we blame Oedipus himself for wanting to find the truth? I believe fate and the gods bear the responsibility for the ruin of Oedipus Rex.
I do not think you can say that anyone is particularly at fault for the tragic things that happen to Oedipus Rex. Laius made a mistake by tryng to avoid the will of the Gods or his Fate. Oedipus is oblivious to all that happens but he did commit the murder of the King, albeit not knowing that the king was his father. It is interesting to note in Edith Hamilton's great work, Mythology, that she records that while Cadmus, the founder of Thebes, and Oedipus' ancestor was favored by the gods, no one in the family had been so favored after him. All of his children came to bad ends but none had been so tragically treated as Oedipus. She gives no reason for this except the vagaries of the Greek Gods.
Oedipus had become the king of Thebes by answering the riddle of the Sphinx.His success in becoming king of Thebes and his downfall in discovering his own origins are the result of the same character trait. In the play, king Oedipus is good in everything . He is so intelligent and potential that he solved the problem of Sphinx and shaved Thebans from the riddle. Likewise he is equally concerned and conscious about the problem of pestilence . But , finally his attempt to serve the citizen brought his own tragic fall to extent that therefore, the audience can should fell pity for the downfall of hero. However ,the hero has a flaw that causes the hero to fail. Therefore, the audience fells an appropriate moral fear that badness leads to bad results. The audience may feel both pity and fear , and neither of them will be corrupting. On the contrary , the emotions will help people sympathize with hroes better than themselves while fearing the negative consequences of wickedness.