Just like in Agamemnon, Part 1 of the Oresteia, the themes of justice and revenge are very closely intertwined. In fact, you could say that the entire point of the trilogy is to tease out the subtle distinction between them. In reading the play, we've got to bear in mind that Orestes isn't hell-bent on killing his own mother (plus Aegisthus) just because he feels like it. Instead, he is doing it out of a deep sense of obligation to his father; basically, he is doing it out of a sense of justice. Not to mention the fact the Apollo told him he had to, or else. This makes us wonder if the gods are even just. If not, what standard of justice can there possibly be in the universe? We certainly don't know the answers to these questions – but Libation Bearers definitely forces us to ask them.
Electra is the most just character in Libation Bearers.
The Libation Bearers shows that Justice, when taken to an extreme, can be highly destructive.