Proof I Am Not Bluffing

When a character deliberately crosses the Moral Event Horizon just to prove a point. Maybe they want to prove that they are willing to make good on a threat, maybe they just want to show that they're not the kind of person you want to mess with. Either way the message is the same: "I'm willing to do this just to make a point, think what I would do if you gave me an reason." Particularly effective when the character harms something he likes (like one of their favorite henchmen), as it shows they will be far less merciful to anything that they don't like.

Anime and Manga

 * In the "Unknown Tales" filler of Bleach,

Film

 * In Ronin, Gregor is not only prepared to, but actually does shoot at a random child in a playground simply to make the point that he is a conscienceless killer who should not be doublecrossed. The man he is dealing with frantically assures him that the demonstration will not be necessary, and pushes away his hand so the bullet misses.
 * In Taken, Bryan demonstrates that he is willing to do anything to get his daughter back
 * A classic staple of James Bond style supervillains; appearing on a huge video screen before the UN to commit an act of wanton destruction just to demonstrate that they have the means and the will to do worse if their ransom is not met:
 * The closest an actual Bond movie came to this was Thunderball. Used the giant screen to make threats, but didn't actually set off any of the nukes, just proved they had them.
 * In the Austin Powers film The Spy Who Shagged Me, Dr Evil blows up the White House to demonstrate his giant moon based laser... except it was actually just footage from Independence Day.
 * The Crimson Jihad in True Lies set off one of their nukes in the Florida Keys as a demonstration.
 * Danny Roman in The Negotiator invokes this trope when.
 * In Pirates Of The Caribbean: On Stranger Tides, Blackbeard tries to coerce Jack into helping him by threatening to shoot his love interest, who happens to be Blackbeard's daughter. When Jack calls him out on it, Blackbeard orders the Quartermaster to bring him six pistols, four unloaded. Jack gets the message fairly quickly. After he leaves, Angelica asks Blackbeard if he knew which guns were loaded. His answer is a not-very-reassuring "Of course, my love."
 * In Star Wars: A New Hope: Tarkin destroys Alderaan with the Death Star to demonstrate the destructive power of the station. In Expanded Universe accounts, this proves to be a colossal political blunder as many planets in the Empire realize that this shows that its leadership is made up of kill crazy psychos who have to be stopped at all costs and the Rebel Alliance gets an upsurge in support.

Literature

 * In The Vampire Files by PN Elrod, Jack Fleming's friend shoots him with a crossbow in front of several of their enemies, partly to invoke this. However, they didn't realize Jack was a vampire, and since he'd deliberately missed Jack's heart, Jack recovered fairly quickly.
 * In The Otherworld Series, the Pack's enforcer Clay doesn't need to fight all that often in order to keep non-Pack werewolves in line, because everyone knows what he did to that one guy...
 * In Knight of Ghosts and Shadows, there's a subversion. When the Merseians fail in an obnoxious plot against the planet Dennitza, Dennitza's Gospodar (monarch) needs some place in the Merseian empire to really splatter, to make sure it's understood that what they did (killing several of his kinfolk, to boot, most of them by the nuking of their estate) is not good behavior. He's naturally unwilling, though, to waste a populated planet. Flandry suggests as an alternative a world he'd found from intelligence probing: it's high in strategic priority, but uninhabited. Thus the Gospodar is able to prove he's not bluffing without being a war criminal.

Live-Action TV

 * The Star Trek: The Original Series episode, "Errand of Mercy," Kor, governor of the occupied planet of Orgainia, demands that Kirk and Spock, who were obviously sprung by the natives, demands they be surrendered and has 200 hostages shot to show they are serious in their demands. Unfortunately for him, the Orgainians are and have no reason to fear, let alone bow to, such threats.
 * In Breaking Bad Gustavo, the main villain and drug lord, brutally slits the throat of his employee just to prove a point to the main characters, Walter and Jesse.
 * In Boardwalk Empire ruthless gambling tycoon Arnold Rothstein intimidates an underling by recounting a horrific story where he bet a man he couldn't swallow a billiard ball, intentionally causing him to choke and die. He ends the story by saying, "Do you know what the moral of that story is? The moral of that story is that if I'm willing to make a man choke to death for my own amusement, what do you think I'll do to you?!"

Newspaper Comics

 * Kind of a subversion in one long-ago Doonesbury strip: a representative of the National Rifle Association thought Duke was bluffing when he leveled a pistol at the visitor. "We both know that pistol isn't loaded," or words to that effect. The pistol wasn't loaded, but Duke didn't know that, and he wasn't trying to prove anything when he pulled the trigger several times. He just thought, Uninvited guy in my house. Shoot him dead. Duke is like that, especially when he's been making use of the wrong sort of mind-altering substances ... which he does on a fairly regular basis.

Western Animation
"Scorpio: Good afternoon, gentlemen. This is Scorpio. I have the Doomsday Device. You have 72 hours to deliver the gold or you'll face the consequences. And to prove I'm not bluffing, watch this. UN Man 1: [all the men look at the explosion] Oh My God, the Fifty-Ninth Street Bridge! UN Man 2: Maybe it just collapsed on its own. UN Man 1: We can't take that chance. UN Man 2: You always say that. I want to take a chance!"
 * Spoofed on The Simpsons in the episode "You Only Move Twice":


 * In G.I. Joe: Resolute, Cobra Commander vaporizes Moscow and its ten million people to prove what his weapon can do and what he's willing to do with it.