Robert Solomon argues (The Joy of Philosophy) that “Vengeance is the original passion for justice. The word ‘justice' in the Old Testament virtually always refers to revenge.” This isn't isolated or primitive: “throughout most of history the concept of justice has been far more concerned with the punishment of crimes and the balancing of wrongs than with the fair distribution of goods and services.”
Of course, vengeance is not always and everywhere right. Vengeance must be controlled, limited, institutionalized. Like other passions, vengeance can get out of control. Sometimes it's right to forego vengeance.
But vengeance is a rational passion, one that is ethically and philosophically defensible. It doesn't have to spin out of control; it can be a “calm passion,” like love. Sometimes, Solomon claims, it's “wholly called for, even obligatory, and revenge is both legitimate and justified. . . . to seek vengeance for a grievous wrong, to revenge oneself against evil—that seems to lie at the very foundation of our sense of justice, indeed, of our very sense of ourselves, our dignity, and our sense of right and wrong.” Vengeance, often taking the form of accountability and punishment, gives us satisfaction that things have been put right.
Vengeance and justice ought not be opposed. Even forgiveness fits into a context of vengeance: “Both the Old and New Testaments (more the latter than the former) also encourage ‘forgiveness,' but there can be no forgiveness if there is not first the desire (and the warrant) for revenge.” Even mercy isn't opposed to vengeance. Rather, mercy is “an attempt to see farther and aim at a much larger sense of satisfaction than vengeance alone could ever provide.”
“Vengeance is mine,” God says. It must be a good thing, else why would He want it?