Did I miss it, or did Cage's character let the lawyer Longdale who organized the whole snuff film to be made off the hook. He hunted down and killed James Gandolfini and the Machine, but ends right there.
I also thought the revenge he enacted on Gandolfini and the Machine was kind of weak considering the torture they put the girl through. You'd think he would've burned Gandolfini alive and not burn him after he bludgeoned him in the head, and the Machine died a rather quick merciful stabbing death considering all the evil things he's done.
Dino (Peter Stormare) killed Longdale with his crossbow. So everyone in that group, except for Cage, was dead by the end. Longdale shoots Dino before he dies, killing him in turn.
As for the other two, Cage had nothing personal against James G and Machine, bar some emotional investment in the matter. He was just a regular family guy, which is why he didn't get creative or torture them to death like a professional. He wanted to avenge Mary Ann and Max, so ending their lives was justice administered. Plus, Machine was trying to kill him so he had no chance to prolong his death with torture.
I guess I blinked and missed Longdale getting killed. One other problem I had with it is why protect the Christian estate from the victim's mother. All she got was an envelope of cash, which couldn't have been more than fifty or so thousand dollars, from Mrs. Christian for her husband murdering her daughter. She should have gotten the whole estate, but I guess he couldn't testify to that without incriminating himself for murder.
He also wanted to kill them. Towards the end of the film Cage was becoming a vengeful, hateful person. When he asked his wife to “save him” he was asking her to save him from his hate.
He wanted to kill Eddie and tried to, but he just couldn't bring himself to cross that line. So he left the room to call Mary Ann's mother and get her blessing. Only then was he capable of reaching the place within himself where he could kill Eddie and Machine. Protecting his family wasn't the biggest part of his reason for killing them.