Perfidy

Per"fi*dy (pẽr"fĭ*d?), n.; pl. Perfidies (- dĭz). [L. perfidia, fr. L. perfidus faithless; per (cf. Skr. parā away) + fides faith: cf. F. perfidie. See Faith.] The act of violating faith or allegiance; violation of a promise or vow, or of trust reposed; faithlessness; treachery.

The ambition and perfidy of tyrants.
Macaulay.

His perfidy to this sacred engagement.
DeQuincey.