The Parker character

What film makers get wrong about the Parker character is that they give him human traits whereas, in Richard Stark's (Donald Westlake) novels, he is a machine. He doesn't do small talk, he doesn't smile, laugh or crack jokes: he is humourless. He talks only when necessary and then, only to progress the robbery at hand. He doesn't 'open' himself to anyone, doesn't have any interest in anyone else's feelings. He doesn't share personal thoughts. He is emotionless, a force of nature devoid of normal human foibles. He is totally self reliant without the need for emotional support from others.
The closest an actor came to a proper Parker was Lee Marvin in Point Blank, although he only became machine-like after 'dying' on the Alcatraz fence.
The Parker character is more like a Terminator than a human being.