The action of betraying someone or behaving very badly towards someone is called perfidy.

背叛某人或对某人表现得非常恶劣的行为称为背信弃义

Would the man's perfidy never reach a limit?

这个人的背信弃义难道永远没有止境吗？

The suspicions of British perfidy were bad enough.

美国人怀疑英国人背信弃义，这已经足够糟糕了。

As devotion unites lovers, so perfidy estranges friends.

投入使得爱人更亲密，背信能疏远朋友。

Perfidy and fraud are the vices of civilized nations, credulity and violence those of the inhabitants of the desert.

背信和欺诈是文明国家的丑行，荒蛮之地的居民则是轻信和暴力。

The disclosures alluded to by Powell were seen by hard-liners in the administration as another sign of Iranian perfidy, and by Europeans as nothing new.

美国政府的“鹰派”政治家将鲍威尔暗自透露的秘密消息看成是伊朗的有一次背信弃义。而欧洲人却对此感到不足为奇。