Driving the Knife

In many a story, there comes a time when the villain does something at his most evil to someone. In other words, the villain metaphorically drives a knife through the audience's heart, propelling the story forward. There are many ways he or she can do it:
 * Killing or inflicting pain on an important character.
 * Leaving the main character to his physical or mental doom.
 * Kidnapping or making off with someone.
 * Imprisoning an important character.
 * Pushing aside another force, like the police.

Examples
Live Action Movies
 * Captain Vidal: Callously smashes an innocent peasant's face with a bottle and in the final climax pulls his gun and shoots his own stepdaughter.
 * Noah Cross: After Jake Gittes unveils his shady motives, Cross manages to escape and make off with Evelyn Mulray's daughter, ending the movie a free man.
 * Edwin Epps: When Patsey is tied to a post, Epps grabs a whip and lashes her savagely.
 * Davy Jones: Turns against Mercer and strangles him with his tentacles.
 * Agatha Trunchbull: Locks Matilda in the chokey until Miss Honey arrives and saves the film's heroine.
 * Miles Quaritch: Guns down the Na'vi settlement while drinking a nice cup of joe.
 * Falcon: Carries Stuart Little to the edge of the Pishkin Building's roof and lets him go, causing Stuart to plummet into a dump truck.
 * Mola Ram: Tears out a prisoner's heart and lowers him down into a pit of boiling lava.
 * Queen Bavmorda: Turns Willow's army, including her daughter Shorsha, into pigs.
 * Judge Doom: Displays his evil nature when dunking a cartoon shoe into a pot of boiling dip.
 * The Rancor: Grabs up a Gamorrean guard and stuffs him into its mouth, consuming him whole.
 * Bill Sikes: Callously beats Nancy with a cane, killing her.
 * Grimm Jim: Guns down Judy's husband, taking over the saloon.

Animated Movies
 * Scar: Ignoring Mufasa's desperate pleas, Scar looks deep into his eyes and hisses "Long live the king", then shoves him over a cliff to his doom.
 * Lots-O'-Huggin' Bear: After Woody and Buzz save his life, Lotso callously leaves the toys behind to fall into a refuse incinerator instead of pressing the emergency stop button.
 * Mor'du: Shoves Merida down and prepares to swallow her whole until Elinor springs to the rescue.
 * Jafar: Turns into a snake and prepares to crush Aladdin.
 * Shan-Yu: Realizing that Mulan interfered with his plan, Shan-Yu grabs up his sword and slashes her across the side.
 * Darla Dimple: Floods Mammoth Studios to get Danny and the other animals booted out of Hollywood.
 * Nigel: Feigns an injured leg to lure Sylvio the guard to come to him but knocks him out with a chloroform rag before bird-napping Blu and Jewel.
 * Muska: Takes Sheeta hostage and makes off with her and the crystal.
 * Charles Muntz: Sets Carl's house on fire and makes off with Kevin.
 * Archibald Snatcher: Makes an attempt to kill Eggs when he seizes power over Cheesebridge; in the climax, after falling into the briehemoth, he grows into a giant monster and snatches up Winnie a la King Kong.
 * Dr. Facilier: Knocks Ray to the ground and treads on him, snuffing out his light.
 * Scroop: Slices Mr. Arrow's lifeline.
 * Stromboli: Locks Pinocchio in a cage.

Books
 * Mulgarath: Turns against the dwarves and sends his goblins to murder them.
 * Polyphemus: When Odysseus and his sailors enter his cave, Polyphemus snatches up two men and devours them.