Benedict Arnold, Brutus, Judas, Judas Iscariot, Machiavellian, Quisling, abettor, accessory, accomplice, archtraitor, betrayer, cockatrice, coconspirator, conniver, conspirer, counterplotter, double agent, double-crosser, double-dealer, exploiter, finagler, informer, intrigant, intriguer, machinator, maneuverer, operator, opportunist, plotter, quisling, rat, schemer, serpent, snake, timeserver, traitor, treasonist, trimmer, turncoat, wire-puller