First half was great

I agree it did feel like a movie that was somehow less than the sum of its parts. It had some very good scenes and the idea was great but it was bogged down by the Duvall parts and the ending was unsatisfactory. Like others have said it felt like we were cheated out of what should have been a normal guy having reached his boiling point who then then takes out his (often justified) frustrations with the world, as depicted, rather than the guy being some psychopath all along. I felt similarly cheated by the film Nobody, hoping this was going to be another normal guy going about kicking ass, but instead it was a guy who we found out had a background for being some assassin.