Medea

Medea, whose name means "the cunning one", was the daughter of the king of Colchis. She was a ruthless sorceress who was something between a witch and a goddess. She was the first wife of Jason who came to Colchis to retrieve the Golden Fleece. It was actually Aphrodite and Eros who caused Medea to fall in love with him as they knew, without her help, he would be unable to perform the tasks her father insisted of him. She did use her magic to aid him in his tasks, and then returned on the Argo with him to Iolcus.
On the way back, with her father's ships in hot pursuit, she cut her half-brother into pieces and threw them into the sea knowing that her father would stop to retrieve them. Iolcus was, at that time, ruled by King Pelias, and Medea tricked his daughters into boiling him, which resulted in his death. Because of this, both Jason and Medea were banished.
Jason went on to take a second wife named Glauce, which really ticked Medea off, and she saw to it that Glauce was given a poisoned wedding dress which burned her skin and killed her. Then she went a little further and killed her own children by Jason. She then escaped to Athens in her grandfather, Helios', chariot and married King Aegeus. This was before Aegeus knew that Theseus was his son, and when he one day showed up in his court, Medea tried to put doubts in her husband's mind that Theseus was not his heir because she wanted her own son by Aegeus to succeed him. But, when Aegeus finally realized that Theseus was indeed his son, Medea fled with her son and returned to become ruler of Colchis.