REVENGE (also vengeance, retribution, or vendetta amongst others) consists primarily of retaliation against a person or group in response to a perceived wrongdoing. Although many aspects of revenge resemble or echo the concept of justice, revenge usually has a more injurious than harmonious goal. The goal of revenge usually consists of forcing the perceived wrongdoer to suffer the same pain that was originally inflicted.

Revenge is a hotly-contested ethical issue in philosophy. Some feel that, at the very least, the threat of revenge is necessary to maintain a just society. In some societies, it is believed that the injury inflicted in revenge should be greater than the original one, as a punitive measure. The Old Testament philosophy of "an eye for an eye" (cf. Exodus 21:24) tried to moderate the allowed damage, in order to avoid a vendetta or series of violent acts that could spiral out of control—instead of 'tenfold' vengeance, there would be a simple 'equality of suffering'. Detractors argue that revenge is a simple logical fallacy, of the same design as "two wrongs make a right." Some Christians interpret Paul's "Vengeance is mine; I will repay, saith the Lord" (Romans 12:19, King James Version) to mean that only God has the moral right to exact revenge. Indeed, every major religious system contains some method for the mediation of disputes and for the limitation of vengeance by imputing a sense of cosmic justice to replace the often faulty justice systems of the world of men.

Of the psychological, moral, and cultural foundation for revenge, philosopher Martha Nussbaum has written: "The primitive sense of the just—remarkably constant from several ancient cultures to modern institutions…—starts from the notion that a human life…is a vulnerable thing, a thing that can be invaded, wounded, violated by another's act in many ways. For this penetration, the only remedy that seems appropriate is a counter invasion, equally deliberate, equally grave. And to right the balance truly, the retribution must be exactly, strictly proportional to the original encroachment. It differs from the original act only in the sequence of time and in the fact that it is response rather than original act—a fact frequently obscured if there is a long sequence of acts and counteracts" ^[1].

In ancient societies, in particular those with weak central justice systems, the method for deterring murder was to allow the victim's family to avenge the killing. However, if the families of the killer and victim disagreed in their moral assessment of the killing, they would most likely disagree as well in their assessment of any revenge actions which were taken, and a blood feud might ensue.

Vendettas or 'blood feuds' are sequences of acts and counter-acts motivated by revenge and carried out over long period of time by familial or tribal groups in a quest for justice; they were an important part of many pre-industrial societies, especially in the Mediterranean region, and still persist in some areas. During the Middle Ages, most would not regard an insult or injury as settled until it was avenged, or, at the least, paid for — hence, the extensive Anglo-Saxon system of 'wergild' (literally, 'man-price') payments, which placed a certain monetary value upon certain acts of violence in an attempt to limit the spiral of revenge by codifying the responsibility of a malefactor. The story of Wimund the Bishop illustrates the typical implacability of the time: its hero, though blinded and imprisoned, would avenge himself against his enemies 'if he had even but the eye of a sparrow'.

In Japan's feudal past, the Samurai class upheld the honor of their family, clan, or their lord through the practice of revenge killings, or 'katakiuchi'. These killings could also involve the relatives of an offender. Today, katakiuchi is most often pursued by peaceful means, but revenge remains an important part of Japanese culture.

The goal of some legal systems is limited to "just" revenge — in the fashion of the contrapasso punishments awaiting those consigned to Dante's Inferno, some have attempted to turn the crime against the criminal, in clever and often gruesome ways.

Modern Western legal systems usually state as their goal the reform or re-education of a convicted criminal. Even in these systems, however, society is conceived of as the victim of a criminal's actions, and the notion of vengeance for such acts is an important part of the concept of justice — a criminal 'pays his debt to society' evinced by countries such as the United States continuing the practice of capital punishment.

Interestingly, psychologists have found that the thwarted psychological expectation of revenge may lead to issues of victimhood.

The first written appearance of the proverb "revenge is a dish best served cold" is often credited to the 18th century novel Les liaisons dangereuses, but since it doesn't actually appear in the original text, the validity of this attribution is unclear.

Revenge has been a popular theme for art and culture throughout history. Examples from the classics include: The Oresteia, Hamlet, The Merchant of Venice, Don Giovanni, The Cask of Amontillado, La Forza del Destino, Moby-Dick, Othello, Titus Andronicus, and The Count of Monte Cristo. Revenge is also a prevalent theme in hardboiled fiction; e.g., Red Harvest by Dashiell Hammett, The Hunter by Richard Stark, several works by Mickey Spillane. Revenge is a prominent theme in contemporary motion pictures as well; e.g., the film (based on the graphic novel) V for Vendetta is an archetypal artistic portrayal of revenge.

• Retributive justice
• Culture of honor
• Duel
• Forgiveness
• Feud
• Compensation (essay)
• Utu (Maori concept)
• Tit-for-tat, a game theory strategy based on revenge/retaliation
• Lawsuit
• fight

• "Bitterness & Vengeance vs. Gratitude & Forgiveness" from Project Worldview