The character expects the opposite of what is going to happen to him in near future. The audiences can understand the characters’ error of judgment of the situation and presume the result beforehand.
Dramatic ironies serve the major purpose of foregrounding the central thematic concerns. In Antigone plenty of instances of dramatic ironies are found. One prime example is the idea of a noble death desired by Antigone. She believes that it is better to die performing the will of God by burying the dead body of her brother. She challenges Creon to face the noble death. Till her final exit, Antigone appears resolute and spirited and ready to face death. But the moment she is led to the tomb, she cannot maintain her same spirited personality and shows her human weaknesses in front of the death.
The expectation of the chorus is also ironic. The chorus expects and prays for the everlasting peace after the civil war in Thebes. They believe that after the reign of Creon, the Thebes will prosper, but they are all unaware that Thebes is soon to face problems again. Creon's failure and ruin at the end is also ironic, because he is quite sure that his fortunes are on the rise after his kingship. Conversely, he concludes at the end that even the mightiest monarch is helpless in the face of destiny.
Creon passes the new law, ignoring the divine law, believing that he will ensure the restoration of stability and peace in Thebes after the death of Oedipus. But it is his foolishness in guessing so as this same law is about to bring a new crisis in the state. This is ironic that his expectation does not meet.