In Antigone, is it possible to choose a tragic hero?

Yes, it is possible, but you do have more than one option because both Antigone and Creon demonstrate most of the qualities of a tragic hero.  In my opinion, Creon fits the title better, but you can make a sound argument for either character.  Here's how:

Antigone
1. Once noble hero/heroine experiencing a tragic downfall--Antigone is the daughter of royalty. As Oedipus's daughter, she is part of the Greek elite and is engaged to the new king's (Creon) son Haemon.  She goes from this high position to being imprisoned, sentence to death, and committing suicide.

2. Tragic flaw--for Antigone, most would argue that her tragic flaw is pride--not necessarily in a negative sense but in doing what she knows is right in the gods' eyes and not wavering from that decision.  However, she does demonstrate some arrogance in her attitude toward Ismene and Creon.

3. Tragic realization--when Antigone is led away and discusses her lonely fate with the Choragos, she realizes that she is going to have to sacrifice her life for her morals. Although she does not believe (or realize) that she has done anything to bring about her own downfall, she does question the unfairness of her situation and even becomes argumentative with the Choragos. Her realization is ultimately that she is going to die for her attempt to obey the gods, and she takes her own life in acceptance of that fate.

Creon   

1. Tragic downfall: At the play's beginning, Creon is the newly crowned king.  He seeks to bring order back to his city and punish those who created disorder.  At first, he seems to have an opportunity to be a good king, but he makes foolish decisions based on arrogance and loses everything in the end.

2. Tragic flaw: Creon's tragic flaw is arrogance/pride. Teiresias, the prophet, even points out the danger of men being too proud. Creon will not listen to wise council or even to his own family members who try to dissuade him from executing Antigone--he wants to make an example out of her. In the end Creon's pride causes him to lose not only his niece but also his son and wife.

3. Tragic realization: Creon fits the role of tragic hero slightly better than Antigone does because of his extensive realization at the play's end.  He considers killing himself because of the deaths that he has caused but realizes that that would be taking the easy way out.  His realization occurs when he takes full responsibility for his decisions and admits that he should have tried to spare Antigone's life.

Good luck on your paper.