Perfidy
Perfidy (pẽr"fi*dy) , noun
[Latin perfidia, from Latin perfidus faithless; per (compare Sanskrit parā away) + fides faith: compare French 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.
His perfidy to this sacred engagement.