Perfidious

a.	1.	Guilty of perfidy; violating good faith or vows; false to trust or confidence reposed; teacherous; faithless; as, a perfidious friend.
	2.	Involving, or characterized by, perfidy.

Adj.

1.

perfidious - tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans; "Punic faith"; "the perfidious Judas"; "the fiercest and most treacherous of foes"; "treacherous intrigues" Synonyms: punic, treacherous

Machiavellian, alienated, ambidextrous, artful, corrupt, crafty, crooked, cunning, deceitful, disaffected, dishonest, disloyal, double, double-dealing, double-faced, double-minded, double-tongued, doublehearted, duplicitous, estranged, faithless, false, false-principled, falsehearted, hypocritical, insidious, mercenary, recreant, shifty, slippery, traitorous, treacherous, treasonable, treasonous, tricky, two-faced, unfaithful, unloyal, untrue, venal