Oedipus Rex

Oedipus' ruin lies in his true relationships with the people around him. He defined himself based on his belief that King Polybos and Merope of Corinth were his parents. He attempted to flee his fate based on this belief. Oedipus kills a man on the road to Thebes; the death itself didn't destroy Oedipus but the realization that the dead man was King Laius and Oedipus' father did destroy Oedipus. Oedipus was punished because he killed a king, not because he killed a man. Because the king happened to be his birth father he also fufilled the prophecy that he would kill his father and later marry his mother. The relationship between the two contributed to Oedipus' ruin, rather than the act of murder itself.
The discovery that Oedipus' wife is also his mother changes his idea of self. Until this realization Oedipus was comfortable with himself and confident in his abilities as king. When he discovers that he unwittingly ran into his fate after all his attempts to avoid it he is disgusted with himself. His relationship as son to his wife and brother to his daughters leads him to stab out his eyes. He goes into exile because his identity has changed; his actions (killing a man and marrying a widowed queen) have not altered but their meaning and impact has. He views his past actions differently now that he knows the full extent of his relationship with his wife and family. By going into exile, Oedipus must now redefine himself based on the relationships he left behind and the lack of human contact he now faces. The people surrounding Oedipus completely changed his view of self as he learned the truth.