retaliate
verb/rɪˈtæliˌeɪt/ 
[intransitive]to do something harmful to someone because they have harmed you first
synonym take revenge retaliate (against someone/something)to retaliate against an attack retaliate (by doing something/with something)The boy hit his sister, who retaliated by kicking him. retaliatory/rɪˈtæliəˌtɔri/
adjectiveretaliatory action