When Odysseus takes his revenge on the suitors, it is not so much out of justice for they do not deserve to die for they have killed no one, but in a manner of war.  To Odysseus the suitors are invaders that need driven out of his “kingdom” and just like when driving out an army, he wants to ensure he won’t be attacked again.  This means he must kill all the suitors.  He was justified not in that justice was upheld, but that he did what he had to do to protect himself and his kingdom.  Had there been a higher authority for Odysseus to plead his case to, he would not have been justified in his actions.  This is exemplified when the gods get involved and Zeus stops his rampage.  The Acts of Revenge by the individual in our day are not justified, because we have a higher authority that we must respect to carry out justice, which sometimes but not always coincides with revenge.