The company took retaliatory action by firing the employee who leaked confidential information.

retaliatory 是形容词，来自动词 retaliate（报复、反击），加上后缀 -ory 构成形容词形式，表示"报复性的、反击的"。 retaliatory action 指"报复性行动"，即针对他人伤害行为采取的回应措施。