Medea by Euripides (431 BCE)

Even by Greek standards, Medea was a complicated woman for whom her magical powers were both a gift and a curse. 

The ever troublesome Aphrodite got Eros to cast a spell on Medea so that she would fall in love with Jason when the Argonauts came to town--which worked like a charm, as the saying goes.  Hera then convinced Medea to help Jason capture the Golden Fleece that her father had dominion over.  So Medea double crosses her father, Aeetes, and contributes to the death of her brother Apsyrtus, making it virtually impossible for her to return to her homeland.  She had burned quite a few bridges, and had demonstrated to Jason that she had some powerful magic at her beck and call.  That is the background to the play.

The play opens in Corinth with Jason announcing that he intends to marry another--Glauce, daughter of Creon, King of Corinth.  He wants to marry up, and he is baffled that Medea would not see this as a big opportunity for their two children.  She would be abandoned, with no homeland to return to and there was no sign that Glauce had any interest in her two children.  So her plan is to muder them, children and all. 

Jason comes off as a clueless and ungrateful idiot.  He would never have been able to capture the Golden Fleece without Medea's magical aid, but he strips her of any role in his telling of his successes.  He also seems to have completely forgotten that she has some powerful sorcery at her finger tips, and she did not hesitate to betray her family, why would he fare any better?  Medea does a wonderful speech about how unfair the gender bias is for women in Greek society (which could have been written at any time for centuries afterwards) and then comlpletely loses our symapthy when she sacrifices not just those who have betrayed her, but also her offspring.  The Greeks do tragedy like no others.