And that is why the Prisoner-No.6 is too perfect, he won't bend, and if you don't bend a little, you'll break! But No.6 doesn't break, if he would only bend just a little, that would make him more human.
It was suggested by the doctor-No.22 in Checkmate that No.6 had a negative reaction to pain, that would take super-human will power. No, No.6 is just too perfect. He might be a trained agent, if his previous job was as an agent for M9, but even the best of agents eventually give in when undergoing long continuous interrogations, coercion, and manipulation. If there is one chink in No.6's armour, it is that he cannot resist a damesl in distress, and No.2 plays on this on more than one occasion, starting with Nadia Rakovsky, and ending in the death of Cathy-No.22.
It is always possible that the Prisoner-No.6 is a symbolc hero figure. But heroes always have faults. As No.6 goes, he is quite rigid. It might have been better if No.6 showed some signs of breaking up, in the way he did during The Schizoid Man. Then I feel No.6 was showing signs that he is human after all. Anyone who is trained not the break, not to crack up, is sub-human. And in No.6 perhaps something human in him is lost, because he is the hero, and heroes never lose. They never break, or show signs of cracking up. No-one could exist day after day in the Village like No.6 did, having to be on ones guard 24/7, 365 days a year for fifteen months. Now that would take super-human will power!