Antigone is a great leader, because of two reasons. First, she was a woman of great courage and principle. A little background might help. In the play, Creon stated that Polynices, the brother of Antigone must not be buried, because he attacked the city of Thebes. Creon also gave a sentence of death to anyone who would seek to bury the body. However, for Antigone to do nothing would bring great shame on the dead body of Polynices. So, what does Antigone do? She seeks to bury the body, even at the pains of death. By this, incredible courage is shown.
Second, Antigone is a great leader because she does the right thing, no matter what. To leave Polynices' body unburied in that context was the height of impiety. According to Greek thought, Polynices would never find rest. So, Antigone commits to a course of action, which is right, even if she will pay the ultimate price.
A person who will do what is right in the face of danger to his or her own hurt is a great leader.