A common theme in The Epic of Gilgamesh and Oedipus is that they are a "zero." Both men have some very bad qualities. For example. Gilgamesh treated people horrible and raped women. The only good thing Gilgamesh did was build the wall. Other than that, he was a horrible person. He treated his workers terribly. Oedipus killed his father and married is mother. Although he was not aware that they were his parents, the fact that he killed someone is a sin. He took is own eyes for what he had done to his father. I guess that was his way of punishing himself?
I attached a video I found on YouTube of somebody reenacting Oedipus killing the King. I thought it was kind of funny.