uses could be as word says "Revenge" or vengeance by treating the person in the same way as he was treated and for some people that vengeance could be a comfort.
             Tragedy (A drama or literary work in which the main character is brought to ruin or suffers extreme sorrow, especially as a consequence of a tragic flaw, moral weakness, or inability to cope with unfavorable circumstances. A disastrous event, especially one involving distressing loss or injury to life). Tragedy basically is the consequence of over passing sometimes the revenge or
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