denounce, give away, bewray, deceive, lead astray, fail, sell, tell on, cheat, snitch, more...

loyalty, faithfulness, trustworthiness

backstab, double-cross, sell out, stab in the back, turncoat, treachery, treason, perfidy, more...

french, little, innocent, poor, purple, latter, turbid, social, false, own, good

break trust,   back stab,   to turn on someone,   give yourself away,   turn on someone,   show disloyalty,   be disloyal,   sell you out,   screw me over,   to turn against