Transformation is a tricky theme in Antony and Cleopatra. Because characters seem to transform at the drop of a hat, the legitimacy of these transformations is always in question. In the end, we’re not sure if the characters have transformed, or merely acted rashly in accordance with their passions. Further, we have to ask whether the characters want to transform, or whether they’re victims of their circumstances.
Cleopatra is not transformed at all during the play. At Antony’s death, her decision to murder herself is just another one of her flighty choices made in passion, without any staying power. It’s only because she knows Caesar will march her in his victory parade that she actually kills herself, not because of the transformation she claims to have over Antony’s death.
Antony is transformed into a lovesick fool by Cleopatra, losing all of his soldierly honor as a result. He must kill himself because this transformation is an irreversible one, and because he realizes that Cleopatra has given him nothing to live for in exchange for his honor.