“What is it?” Torian replied, watching Tiger with a worried expression. Not too worried though, since her flaming crown had disappeared the moment she had doubled over in pain.
“The enemy temple! It's on fire!” the voice shouted.
“Huh?” He involuntarily looked down, and then kept looking, his eyes growing wider and wider. Something underneath the waves was burning bright enough to make them shine like the setting sun. “I- I can see that.” He looked up at Tiger, his expression begging for an explanation. “What are they burning?”
“Yes, you already told me that!”
“You don't understand! The stone is on fire! Underwater!”
Torian blinked. So did most of the youma.
“By all the dark gods, it just crashed and now the sand is burning too! Look at it!” another warlock shouted in the background.
“I think even the water is on fire,” the first one muttered in a voice that bordered on religious rapture.
“Don't be silly,” Tiger interrupted. “The water is too busy exploding to be on fire!”
“I... I stand corrected.”
That is all.
Mister Cynical's Lycanthrope series on fanfiction.net (loosely based on Neon Genesis Evangelion) is notorious for this, to the point where the characters in the series actually come to expect it. One notable example is where Shinji is supposed to kill a member of Seele in Paris. Instead of simply shooting him, he decides to blow up the building he's in, along with many others (including the Eiffel Tower). The end result is that Paris is filled with flaming debris which just happens to form a giant smiley face a mile and a half wide.
Shinji: Now those Frenchies have a smile they can be proud of!
Also, Finishing The Fight (found on the Halo Fanfic Recs page), in which much care is taken to describe the effects when "modern" UNSC weaponry is used on Dungeons & Dragons baddies..
Garrus. Need to question some criminals? Knock down the wall of their warehouse with a cargo hauler and shoot them all in the knees. Turns out they're not the ones who have what he needs to know? Knock down the next warehouse's wall with a cargo hauler and kneecap the men inside. Need to question a mercenary boss? Blow up his car with a tank.
Apparently, Admiral Nick "Havoc" Parker is known for this - according to Shepard, orbital bombardment is his first resort. The prospect of him and Garrus being in the same room is terrifying.
XCOM: Second Contact has X-COM's battle with the Turian patrol at Relay 314. The Turians have one cruiser and five frigates. X-COM brings 400 fighters, 12 cruisers, and 2 dreadnoughts.
In a crossover RPG (Fanon or Canon), Ancient Equivalents have invaded a faction on the level of the Ori (Tech, not power), and they have A LOT of drones (SG Fans Look Them Up), the defending forces just fired 'Vortex Beams' (Derived From Vortex Generation off of B5 Jumpgates) from the their ships, there were to many vortexes (700) that went critical resulting in the loss of a planet, two moons, 125 Ancient ships and 700 defensive forces. The vortexes merged and created a anomaly about 3 LS across :( Let's just say the person controlling the Ancients is not happy that they lost 1/3 or their fleet in the blink of an eye. The defending faction has something called a Planetary Defensive Grid well, you figure it out...
From Gods Of This New World: "Meanwhile, L had been in a harrier jet overhead… He readied a missile to be fired, and unleashed fiery hell on Mello."
In chapter 15 of Ace Combat: The Equestrian War, Flare Star reported (having witnessed it firsthand) that Blueberry was beaten to semi consciousness by four griffins before one of them ripped the wings off her body... Even after she hit the ground, her killer still smashed her spine to make sure she won't get up again.
From Strawhat Theater 2: Our Mrs Monkey: Absalom kidnaps and tries to forcibly marry Nami who's married to Luffy. Luffy uses Gear Second to punch him through several walls. And when Absalom turns invisible, Luffy uses Gear Third to punch the entire room through the rest of the castle.
The Witty Phantom's plan to defeat Stan in their rematch in Yu-Gi-Oh! The Thousand Year Door Redux is basically this. He summons Dice Reaper and uses his own Deckamster ability to make it unkillable by card effects. He then uses the Dice Reaper's effect to rig his dice rolls by basically getting to choose what number he would roll instead of actually rolling dice. By using Take a Chance's effect to multiply his life points by five by rolling a six, the Phantom's life points go from 6,500 to 795,000. But the overkill part is the Phantom summoning Ancient Sacred Wyvern, who gains Attack Points equal to the difference in Life Points if its controller has more than his opponent, resulting in a monster with 780,500 Attack. It fails due to Stan's facedown, Magic Cylinder.
In The Jaded Eyes Series when it's Harry's turn to fight the orcs during the Triwizard Tournament. The task is just to "use any means to retrieve the gold pieces" and Harry does just that... by slaughtering them all and picking their corpses.
The Albacore crew in The Nowakverse has the so-called Darned Nearly Recoilless Rifle. .22 rimfire ammo doesn't sound like overkill until you realize that the Recoilless is used by small rodents for whom .22 is about as large as a 155mm howitzer is for humans. It is shoulder-fired, and it requires a second rodent to reload it from behind. Nevertheless, the Recoilless is used as an anti-personnel weapon.
XSGCOM has this as the X-COM's SOP. Their reaction to most things is to nuke it, or if it's not enough then nuke it with bigger nukes. And if that's not enough, ask Tollans for even bigger ones.
Taken Up to Eleven in the upcoming XSGCOM: Multiverse. The United Galaxies Ship ''Arthur Pendragon'', the one of it's kind X-306 class Dreadnought. 1.75 Kilometres from stern to bow, 65 million tonnes of mass, the ship features an Arcturus Reactornote Based on the abandoned Project Arcturus, four Zero Point Modules, 12 Neutrino Ion Generators and 24 Mark IV Naquadah Reactors for power generation, a Lantean Wormhole Drive, an Asgard Intergalactic Hyperdrive, a Graviton Pulse Drivenote For sub-light propulsion, a Time Jumper Drive and an Alternate Reality Drive. The ship is built around a Lantean Particle Cannonnote The kind found in the Lantean Defence Satellite and has two Ori Energy Beam Weapons, four "Ripper" Heavy Staff Gatling Cannons, four Tollan Heavy Ion Cannons, eight Asgard Plasma Beam Weapons, 16 Ori Pulse Weapons, 36 Railguns, 48 X-COM Laser Cannons, 48 X-COM Phaser Cannons, four Ancient Drone Launchersnote 500 drones each, four VLS missile batteriesnote 100 missiles each, armed with Mark VIII 1.2GT warheads, 16 Horizon Missilesnote 6 x Mark IX 800 GT warheads, eight Tollan "Chicxulub" Class Phasing Bombsnote 100 Teraton Yield, four Tollan "Serita" Class Phasing Bombsnote 100 Petaton Yield and two Tainted ZPM Warheadsnote For taking out stellar systems for further armaments. It also sports improved Asgard Shields as well as a Lantean City Ship class shield and has a hull made of laminate of Kull-Warrior Armour weave, Trinium/Cydonium alloy, Aqua-Plastics and mono-molecular fibre mesh. Additional systems include a Lantean Cloaking Device, Tollan Phase-Shifting Device as well as Asgard Transporter Beams.
In the Stargate SG-1 fanfic Far Beyond Normal, Lt. Colonel Fenton of SG-13 uses "over a hundred people" of whom "even the ambulance drivers and helicopter pilots were Special Forces trained" to capture an unarmed 18-year old human girl loose in Colorado Springs. He reflects that "One of the things he loved about the SGC was that nobody minded if it took a sledge hammer to drive home a nail, so long as the sumbitch got drove." The girl in question turns out to be Buffy Summers, so in hindsight it was just-barely-enough-kill.
In Mega Man Recut, Wily decides the best way to deal with a shrunken Mega Man is a submachine gun.
in Mega Man Reawakened, Robert at one point uses a Program Advance to destroy a breakable wall. There's nothing left of it when he finishes.