Antigone is not really a psychological drama "about" a single character. It is a play about the conflict between characters and more generally about the conflict between human and divine law.
The question of which character is the "protagonist" (literally "first contestant") of the play has been widely debated. There is no single correct answer, as solid arguments can be made for both sides of the debate.
While modern audiences tend to sympathize with Antigone, there is some evidence that Creon would have been considered a protagonist in antiquity. The tragic hero is characterized as one suffering a reversal of fortune followed by some recognition of a truth or insight. Antigone is a somewhat flat character, taking a consistent position throughout the play, while Creon suffers a more traditional reversal and eventually repents of his actions, albeit too late. Thus, Creon follows a more typical pattern of a tragic hero than Antigone and is somewhat more likely to have been considered the protagonist.