Corus From the Multiverses FCP completely and utterly obliterates Perfect Darkness, calling upon his other personality's inter-dimensional horde of boltzmann brains to destroy him.
Survival of the Fittest, to the point where some wryly observe it's almost a competition to see who can fabricate the most over-the-top, graphic death possible.
Jin Li-Jen being practically ripped to shreds by Walter Smith (eviscerated, castrated and decapitated).
Kara Holmes. Villain Blood Boy slices off her foot, shoves it into her mouth, breaking her jaw and blows the aforementioned jaw off with firecrackers before leaving her to suffocate.
Rick Holeman, who gets shot, stabbed, then stabbed again, and again, and again, basically mutilated by the time the fight is over. It's rather Justified Trope, however, seeing how incredibly hard he was to kill.
Red vs. Blue: Reconstruction: after he's already killed Agent South, Agent Washington goes on to dispose of the body by shooting at it, incinerating it, and detonating a bunch of exploding crates next to it. This is apparently standard procedure.
In Linkara'sLet's Play of Star Trek: Voyager: Elite Force, he gets freaked out by small rodent-like enemies and chases them around with a handheld Photon Torpedo launcher. After blasting them (and getting hit with a little splash damage), he muses "Maybe that was a little too much", followed by a caption that reads "But totally worth it."
In the second RP of Darwin's Soldiers, Shelton empties an entire pistol magazine killing Delta Leader. Justified, since he doesn't know how to use a weapon, and an unspecified majority of the bullets missed.
The displacement cannon from Orions Arm is absurdly powerful. It fires a "bubble" of compressed space-time that is the size of an atom, infinitely maneuverable and travels at the speed of light. When it reaches the target it travels between the molecules in its armor and then collapses to release an swarm of monopoles that convert the mass of the target directly into energy, virtually assuring its destruction. How much overkill is this? A single displacement cannon destroyed a fleet of 10000 ships in four seconds.
In A Robo Western, This is how the Sheriff Bot deals with One Eye.
A good example would have to be using SCP-272 on it. SCP-272 is a iron nail that, in the proper conditions, pins someone's shadow to the ground and will not let it go. If the shadow's length is forcefully changed due to the environment, it will pull the person closer to it to keep the shadow embedded under the nail. Thus, if the shadow is changed quickly enough, you can expect the subject to be thrown a large distance. The SCP Foundation decided to use (quoted from the linked page) "a circular array of thirty (30) two-thousand-watt (2,000W) stadium lights" to enact such damage on a large scale. "All thirty stadium lights are then switched on and off in random stroboscopic 'disco' pattern, at 4 Hz. SCP-682 is forcibly hurled around the enclosure in random directions, in accordance with the stroboscopic pattern, and sustains heavy damage." After 55 minutes of this, SCP-682 had sustained damage including 63 broken teeth, severance of its back-left limb, and "its skull has been fractured to the point that both its eyeballs have been dislodged from their sockets." It then evolved luminescence brighter than the stadium lights to nullify its own shadow.
Another good example is having SCP-682 fight against SCP-096. SCP-096 is a small humanoid figure that utterly annihilates anything that sees its face. They battled for twenty-seven hours before the screaming stopped, and both were heavily damaged. SCP-682 lost 85% of its mass. Neither entity would even look at each other after that.
The Protectors of the Plot Continuum have the Canon Bomb. This weapon causes powdered canon to scatter through a badfic-warped location, literally rewriting it into its correct form and dissolving every uncanonical character or object caught in the very wide blast area. Used only once for now, probably because the Agents who used it nearly got vaporized themselves (as they're not canon too).
Whateley Universe: Team Kimba's plans to stop Dark Tennyo in their holographic simulation training. One plan ended up with fifty blocks of (simulated) city utterly destroyed. One plan ended up wiping out the Eastern Seaboard of the U.S. and plunging the Earth into nuclear winter.