Reading through "Agamemnon," which I'm certain I read in college and I'm a little surprised by my reaction. I have a lasting impression of Clytemnestra as the villain of the piece along with her lover Aegisthus. This reading I understand much more clearly Clytemnestra and can even summon up a little bit of sympathy for Aegisthus--at least so far as their crime against Agamemnon. The sacrifice of Iphigenia tore out a mother's heart--destroyed her completely. And what happened to Thyestes (Aegisthus father)--being fed his own children by Atreus (Agamemnon's father), certainly explains some things, even if I am not into the generational vengeance thing. I used to think them the villains of the piece but this speech by Clytemnestra pretty much sums it up:
So now you sentence me to banishment,
allot me hatred, rumbling civic curses.
Back then you offered him no opposition
when he, as casual as at one death
among the crowding and luxuriant flocks,
sacrificed his own child, my dearest birth-pangs,
to conjure up some blasts of air from Thrace.