I’m sure everyone can think of a personal experience where this word applied.

perfidy (per·fi·dy): / pur FI dee /
noun

(1) deliberate breach of faith or trust; intentional treachery; faithlessness
(2) an instance or act of treachery, deceit, or faithlessness

[From Latin perfidia meaning “faithlessness,” from perfidus meaning “through (beyond the limits of) faith,” from per- (“through, beyond”) + fides (“faith”).]

Usage: [via] Supping at the table of corporate America filled my pockets, yet 30 pieces of silver betray perfidy of my soul now crying in the emptiness.