No commentator so far has referred to the opening of the film where Demarre and his son find themselves unwitting witnesses of a robbery and one of the 'braquers' apparently shoots Demarre and his son point-blank, though Demarre re-appears later (How much later?) alive and unharmed to join Vigilante. That's not the only unexplained event. Who was the silent woman with him on the park (Nursing home?) bench? His wife, lover? And the phone-caller who had somehow found his number? Why was he so adamant about not having his hotel room cleaned?
Leaving his overall motivation open to conjecture gave an added interest to the plot, but things left unexplained without the slightest clue as to their significance in the story are merely irritating.
Dupontel is tremendous. He has enormous presence and the rest of the cast, camera work, production and of course, direction, superb.