The entire premise of the film should instantly qualify as this for parents.
Keller's character over the course of the film. It's terrifying to see how a simple family man can go from a friendly human being to a vengeful and paranoid psychopath.
Not helped by the fact he's played by Hugh Jackman.
The crates in Bob Taylor's house. While there are no bodies, the sight of bloodied children's clothes and snakes stuffed in the crates should at least unsettle you in some kind of way.
The torture of Alex Jones. The torture scenes had to be re-edited to earn an R rating from its original NC-17. Even with them edited down, it's still horrifying to watch the pain Alex goes through, ranging from beatings to being boiled in burning hot water.
Probably the worst instance is when Keller comes very close to slamming a hammer into Alex's hand. For a few seconds, you believe he's going to do it, and cringe in anticipation for it. He doesn't, but you realize that you know he would've done it, which in itself is utterly terrifying.
The slow reveal of Alex's face after the torture, which was initially hidden behind the broken sink as Nancy (Joy's mother) carefully removes the burlap sack. His face is utterly soaked in his own blood, and his eyes, nose, lips are swollen and cut to the point where he doesn't look remotely human anymore.
The Reveal of what kind of person Holly Jones truly is. And then there's that pit of hers she keeps hidden in plain sight...
Melissa Leo's acting. Her performance would have Heath Ledger's Joker quivering in fear.
Plus the Fridge Horror that the police unknowingly returned Alex to his kidnapper and torturer because they believed that she was his legal guardian.
The black fluid Holly makes Dover drink.
Loki’s Drives Like Crazy moment, where he’s zipping through heavy traffic at night in wet weather with a child in the backseat, who is dying from an induced drug overdose from the Big Bad, and a goddamn bullet graze on his forehead, the latter of which is giving him grief with blood dripping into his eye and his vision being blurred from the impact itself. Tense does not even begin to cover it.
