- When Alex takes the pet rabbit belonging to the daughter of her lover Dan Gallagher and boils it alive in a pressure cooker. This grotesque act of evil was chilling enough to earn an entry on the Moral Event Horizon page, has given many people who watched it some serious nightmares, and was enough to coin the phrase "bunny boiler" for Yandere-types soon afterwards.
- The scenes where Alex kidnapped Dan's daughter. You can really feel Beth (Dan's wife) complete panic as she runs around searching for her daughter. It's the epitome of every parent's worst nightmare—that your kid could so easily go off with a stranger despite your multiple warnings otherwise, that the stranger could be some perfectly normal-looking person rather than the psycho that they truly are, and though she returns the little girl unharmed, let's face it, she could have harmed her if she wanted to. It doesn't help that there are Real Life cases that have started out like this.
- The climax where Alex shows up in the house to try and kill Beth. Before she attacks her, as she's talking about how resentful she is of Beth, she unknowingly starts cutting herself in the leg with the knife she's holding. It all finally escalates when Alex finally snaps and screams, "YOU'RE A STUPID SELFISH BITCH!" and attacks.
Nightmare Fuel / Fatal Attraction