In looking into this question, one must consider the entirety of the story of Oedipus. Fate led Oedipus into fullfilling the prophesy of the Oracle of Delphi. He does not knowingly kill his father and marry his mother. His quest for the tuth leads him to the discovery of his identity.
Creon tries to make the best of a bad situation but by taking sides in the feud between the two sons of Oedipus and Jocasta, he brought down the wrath of the gods. To leave a body unburied was an offense to the gods and Etocles had violated the terms of the agreement to rule Thebes.
Antigone felt it was more important to follow god's law rather than man's law aka Creon's law. Her reasoning was simple, it was better to break man's law than god's law because gods were much more powerful than kings.
It can be argued that Creon is the tragic hero because he displays hubris in defying the law of the gods, but the true tragic hero is Antigone because she is willing to give her life for her principals and her love of her brother.
You will probably experience many different answers to this question. If we define tragedy as a setting where there is a sense of character evolution through predicaments of pain, I would say that Creon is probably the most tragic of figures in the play. Antigone does not waver nor change throughout the course of the play. She is as committed to her brother's burial rights at the start as she is at the end of it. She operates as the moral compass by which all individuals can analyze their own sense of right and wrong. In contrast, Creon is a figure that remains committed to his idea that justice is found in the law, his laws. His unwillingness to budge causes great pain to his own family, forcing him to witness the death of loved ones, and experience a sense of loss and understanding that was not evident at the start of the play. His sad condition at the end is one that is accompanied with understanding and wisdom. The fact that such attributes come with such extreme cost is what makes him tragic, in my mind.