One way of thinking about Ancient Greek tragedy is about the danger of excess, the danger of going beyond the ethics of moderation, staying within limits, following reason, which we find in various forms across antique ethics. That is one way of understanding tragedy, the dangers of excess and the need to stay within limits. Oedipus would not have accidentally killed his father and married his mother if he had not been excessively angry with the stranger at the crossroads, the stranger who was his father and who he killed. The cycle of killing in The Oresteia, during the trilogy and in the backstory could have been stopped if someone had restrained themselves from killing in passion. If Phaedra had not told her servant woman, in a moment of excessive conversational frankness, of her love for her step son, a lot of bloody excess would have been avoided.
However, if Oedipus had not pushed the boundaries of curiosity, against the wishes of Tiresias, he would not have saved the city from the plague brought on by his polluted presence. Tyranny would have ruled in Mycenae if Clytemnestra had not killed Agamemnon, and Orestes had not then killed Clytemnestra and her lover. The emptiness of kingship would not have been exposed in Phaedra had not initiated a feud between Theseus and Hippolytus.
Tragedy does not refer to the error of avoiding moderation, of avoiding good judgement itself. It refers to those situations where excess is necessary to disrupt patterns where injustice is done and human flourishing is deeply weakened. Tragedy looks forward to a world of civic virtues where disputes are mediated without violence, where rational speech dominates. It also sees that the civic culture itself rests on the pushing of boundaries which brings us back to the extremes of pre-civic heroes. Oedipus becomes a god, or so Oedipus at Colonus hints, because only extremes of action and passion which strain at human limits enabled Oedipus to destroy the Sphinx attacking Troy, to then discover the truth of his pollution, and then to remove himself to avoid that pollution. The power of kings could only be challenged by the fanaticism of Antigone. The destructive behaviour of the gods is brought to light by the paranoid jealousy of Creusa which nearly leads her to kill her son Ion.
Where is the virtue in moderation, in staying within boundaries? Virtue must include the possibility of extremes of passion. The legal civic solution to conflict which is offered in tragedies as desirable could never resolve all conflicts. Tragedy should not be taken to given a moral basis for more and more redemptive violence. It certainly does suggest though that the limit should sometimes be passed and that unwillingness to contemplate this displays lack if virtue, that is human flourishing, strength of character, if we thin about what virtue means for the ancients and can mean now.