Well, he certainly had us fooled. You know, except for those moments of blatant foreshadowing. O’Brien ends up being a more poignantly hated antagonist because we once trusted him. There’s a reason the ninth circle of hell is reserved for traitors. (See Dante’s Inferno.) Other than the treacherous bit, the whole pushing-the-buttons-on-the-backbone-stretching-machine thing qualifies him for the antagonist position just fine.