Problem
The protagonist is the one that takes the main part in a drama. The title of an ancient play, which may indicate the protagonist, is not always the title originally given by the ancient author himself but by a reader, centuries later. If you yourself then were giving a title to the play Agamemnon, would you name the play Agamemnon, Clytemnestra, or The House of Atreus? Why your choice of title/protagonist, and not specifically the other choices?