You have to give it up for Medea: she brings the body count. We first met Medea as the woman who helped Jason (the Argonauts guy) in his quest for the Golden Fleece. Once that was taken care of, they got married, but not long afterwards Jason spotted an opportunity to trade up by marrying the daughter of Creon, the king of Corinth. So he kicked Medea to the curb. Like the song says: so much for her happy ending.
After that shabby treatment, you'd think she would have had trouble seizing the low moral ground, but not our Medea. There are many versions of the story, but in the most famous one by Euripides, Medea sends a gift of poisoned robes to Jason's new bride, who subsequently dies in agony, as does Creon, who tries to save her. Not even winded, Medea then heads offstage to stab her children to death with a knife. She exits with these words:
By the avengers that in Hades reign,
It never shall be said that
I have left
My children for my foes to trample on.
Nope, it never shall be said.