Thwarted Coup De Grace

"..If a man has you at his mercy, then hope like hell that man is an evil man. Because the evil like power, power over people, and they want to see you in fear. They want you to know you are going to die. So they'll talk. They'll gloat. They'll watch you squirm. They'll put off the murder like another man will put off a good cigar. So hope like hell your captor is an evil man. A good man will kill you with hardly a word."

- Terry Pratchett, Men At Arms

Oh, no! The villain has beaten the hero in a fight! Our hero is down on the ground, battered, bloodied and helpless. The villain triumphantly raises his weapon, delivers his gloating one-liner. This is it, our hero is done for! The Big Bad gleefully readies the Coup De Grace...

...and dies.

There are two general ways that this happens. Either the hero pulls some last-minute trick out of his sleeve and delivers the killing blow to the villain, or one of the other Big Damn Heroes leaps in from Behind the Black to finish off the baddie himself.

If the good guy has the bad guy at his mercy, then a Sword Over Head is the usual result. In that case, the hero will either stop himself or go through with it. The distinction between the two is that the good guy almost always gets to make the choice himself and live with the result. Occasionally, somebody else will kill the bad guy, either while the hero is thinking it over or just after the hero decided he couldn't do it. This will often happen eventually if the game makes use of a Coup De Grace Cutscene. May be the result of a successful Diagonal Cut.

Types of Thwarted Coup De Grace:
 * Bait and Switch Gunshot
 * Sword Over Head

Anime and Manga

 * In Naruto, at the climax of a heated battle between Sasuke and Itachi, Itachi has Sasuke cornered and is about to take Sasuke's eyes (and the Psychic Powers they impart) for his own. Itachi touches Sasuke on the bridge of his forehead... and then keels over, dead.

Film

 * Lurtz, the head Uruk-Hai in the movie version of Lord of the Rings: The Fellowship of the Ring, has shot Boromir full of holes and is ready to deliver the killing shot when Aragorn leaps in and kills Lurtz. This gives Boromir enough time to deliver his dying speech.
 * The climax of the Battle of Cowpens at the end of The Patriot has Colonel Tavington ready to deliver the killing strike to Benjamin Martin. Martin ducks under the sword and impales Tavington on his bayonet.
 * Star Wars Episode III: Revenge of the Sith has Mace Windu having just beaten Chancellor Palpatine in a lightsaber duel. Anakin charges in and tells Windu not to finish Palpatine as Palpatine is begging for his life. Just as Windu is about to Kill Him Already, Anakin hacks Windu's hand off and Palpatine breaks out the Force Lightning.
 * In Episode II, Dooku brings down Obi-Wan, but before he can deliver the final blow, a previously electrocuted Anakin gets better and jumps across the room to block it.
 * Episode VI: Palpatine uses Force Lightning again, this time on Luke, and Vader stops him. Unusual in that it doesn't involve any weapons.
 * In Gladiator, Emperor Commodus has ordered General Maximus to be executed. The soldier orders him to kneel so he can stab him. Maximus (with his hands tied) head-butts the soldier, takes his sword and then kills every other soldier who was guarding him. Maximus is Badass.
 * Serenity does this twice with Mal's confrontations with the Operative. The first time, Mal is surely beaten, and the Operative is about to finish him off with his sword when Inara's flashbomb goes off and stuns him. The second time, the Operative is about to kill Mal after having paralyzed him by grabbing a specific nerve cluster.
 * In Highlander, Connor MacLeod's first death nearly his final as the Kurgan prepares to deliver the beheading shot, only to be tackled away by Conner's kinsmen.
 * Not to mention The Kurgan gets distracted in their final Sword Fight when he's about to take MacLeod's head because of the intervention of Connor's Love Interest.
 * In Robin Hood: Prince of Thieves, the Sheriff beats Robin with his father's sword and has Robin backed against the wall. The Sheriff turns to Marian, says, "Get ready", only to have Robin pull Marian's dagger out of his boot and stab the Sheriff.
 * In the final duel of Rob Roy, Archibald Cunningham has Rob at his mercy and pauses to remind him that no quarter would be asked nor given. Rob grabs onto Archie's blade, preventing the dainty fop from delivering the killing blow, and hacks him nearly in two.
 * Happens to Frollo at the end of The Hunchback of Notre Dame as a result of him saying "And he shall smite the wicked and plunge them into the fiery pit!" while attempting to kill the heroes.
 * Bonus points for falling to the flames he started to kill one of the protagonists.
 * Happens in Transformers Dark of the Moon TWICE within 10 MINUTES of each other. First with Bumblebee, then with Optimus.

Literature

 * This happens in A Song of Ice and Fire during the duel between.

Web Comics

 * Happens twice in this Order of the Stick episode.

Western Animation

 * Batman loves this trope. The Riddler hates it. Batman once used this to save the Riddler's former lab partner that was suspected of sabotaging a brain enhancing disk.
 * Used in the climax of The Secret of NIMH when Justin has thrown out his sword and is giving a speech, Jenner sneaks up behind waiting to make the strike, by the time Justin notices Jenner has him, suddenly Jenner gets stabbed in the back,.....by a Mook he just stabbed.

Live Action TV

 * In the Buffy season 2 finale, Angelus has seemingly defeated Buffy in a sword fight. He goes to finish her off and she catches the blade between her hands.
 * Heroes does this, though sometimes with a role reversal. Two good examples come from near the end of Season 2: HRG/Noah has at gunpoint, and pauses to remark about how if he just pulls the trigger it will all be over. Then, later, Victoria has  at the end of a shotgun. Knowing he can regenerate, she says, "I knew it would take blowing your head off. Better late than never." Neither was successful, largely because they ran their mouths when they should've been pulling the trigger.
 * "What am I thinking now, Parkman?"
 * In Stargate SG-1 this happens in the episode The Warrior when Teal'c kills
 * In an episode of Babylon 5, Londo's old friend, who is accused of treason without proof, challenges him to a duel for supposedly conspiring against him. At the end, he has Londo on his knees, raises his sword for the final blow, and hesitates a split second, which is all Londo needs to stab his opponent in the gut. After the fight, Londo reveals to Vir that his friend threw the fight, as he was always better, in order to allow his family to escape disgrace. By rules of the combat, the victor assumes responsibility for his opponent's family. As such, they are now Londo'a family, so the accusation of treason won't harm them.

Real Life

 * In one spectacular MMA bout, fighter Pete Sell landed a powerful, devastating body shot to opponent Scott Smith's liver. As Smith doubled over in agony, Sell rushed in to finish the job with his hands down, giving Smith the opportunity to deliver one last knockout punch. Smith won the fight, right before keeling over for medical attention.
 * The most famous sports-world example is the Miracle at the Meadowlands, in which the Giants had the lead, had possession of the ball with less than thirty seconds left in play, and their opponents the Eagles had no timeouts, and yet somehow the Giants still lost the game.
 * Similar to the MMA bout above, in 2004 future boxing world lightweight champion Nate Campbell badly hurt his opponent Robbie Peden with a body shot, doubling Peden over and causing him to stagger around the ring. Peden was able to defend just well enough for the next 30 seconds or so to evade or block Campbell's attempts to finish him, and recovered enough to finally punch back. Campbell, in his arrogance and certainty of victory, stood in front of Peden with no defense at all and dared Peden to hit him again. Peden did, and Campbell fell over backwards like a tree going down. Link.