a situation in which you do something bad to somebody because they have done the same to you 以牙还牙；针锋相对；一报还一报 the routine tit for tat when countries expel each other’s envoys 国家相互驱逐对方使节这种惯常的报复行动 tit-for-tat assassinations by rival gangs 敌对团伙冤冤相报的暗杀