Character development of Oedipus from Oedipus the King through Oedipus at Colonus

Write an essay in which you trace the character development of Oedipus from Oedipus the King through Oedipus at Colonus. Cite the key plot events that mark his journey. What does he achieve in the course of his life ? Why does Sophocles consider him a tragic hero who has much to teach us ? What do you learn from him (Oedipus)?