perfidy
他的背叛行为彻底摧毁了我们之间的信任。
His act of ___perfidy completely destroyed the trust between us.
他的商业伙伴的背叛行为东窗事发，原来他偷偷将客户转移到了自己的公司。
His business partner's ___perfidy came to light when he secretly transferred clients to his own firm.
历史记载了那位将军的背叛行为——他在深夜为敌人打开了城门。
History records the ___perfidy of the general who opened the city gates to the enemy at night.