retaliation
Hurting someone back after they hurt or wronged you.
Retaliation means responding to something harmful or unfair by doing something harmful back. When someone retaliates, they're essentially saying “you hurt me, so I'm going to hurt you back.”
You see retaliation in everyday conflicts: if your brother breaks your favorite toy on purpose and you respond by hiding his soccer ball, that's retaliation. If someone spreads a rumor about you and you spread one about them in return, that's also retaliation. The key element is that you're responding to a wrong by trying to even the score.
Retaliation can happen on larger scales too. Countries might impose retaliatory tariffs after trading partners raise prices on their goods. Throughout history, cycles of retaliation between groups have turned small conflicts into long, destructive feuds.
The word has a negative connotation because retaliation usually makes problems worse rather than solving them. When someone retaliates, they often justify it by thinking “they started it,” but the other person probably feels justified in retaliating again, creating an endless back-and-forth.
Retaliate is the verb form: “She decided not to retaliate when her classmate was rude to her.” Breaking cycles of retaliation takes real courage and wisdom.