Characters in Antony and Cleopatra often have to choose between being loyal to their ideals and being loyal to their circumstances. Loyalty is central to a lot of the relationships in the play, but betrayal always hangs near as a frightening fact when so much power is at stake. Characters’ loyalty to one another is constantly called into question by their quick betrayals of one another, and the question of whether loyalty is an enduring feeling is raised as a result.
Antony decides to commit suicide at the end of the play because he has betrayed his own honor. In spite of all the other things that have happened, he most regrets his failure to be his most noble self. The realization that he hasn’t been true to his own ideals is the blow that kills him.
Cleopatra is never loyal to Antony, even though she claims to kill herself over him. Her constant willingness throughout the play to manipulate him is an indicator of the fact that she’d betray him as soon as it was convenient for her, either politically or emotionally.