Nosfera's husband Brahm, a vampire, is killed by being stabbed in the heart with a cross. This is lampshaded.
Schlock Mercenary takes this to heart, especially Kevyn, who wears antimatter grenades on his shoulders. One of those antimatter grenades is capable of slagging a tank, and the other has the yield of a good-sized nuke.
Schlock himself runs around with two sawed off anti-tank multicannons and an oversized plasgun. The multicannons are especially ridiculous because he can hook up feeders and, quote, "fire breacher rounds on full auto."
One of the most popular books with mercenaries in the Schlockverse, The Seventy Maxims of Maximally Effective Mercenaries, contains several appropriate quotes on the subject, as shown in the quotes section for this trope. The one that quotes this trope practically verbatim can be found in poster form.
Actually subverted on one occasion, in which Schlock mocks two enemies for aiming anti-tank weapons at him. They tell him that they're not worried about a little overkill, to which Schlock responds, "Actually, I was worried that you might want to be pointing your anti-tank weapons at, say, incoming tanks." Incidentally this wouldn't have been overkill, he can't be killed by explosions if his friends find even most of the pieces.
Schlock's immune system is itself a form of overkill, it allows him to survive practically anything, even including foreign nanites.
Once, the PD Fleetmind launched an all-out assault on an entire star system as a diversion, to extract Tagon's Toughs with minimum collateral damage. To quote the UNS Marine prize crew guarding the Toughs: "'Minimal collateral damage' and 'entire star system' do not belong in the same sentence"
The fishing boat captain in Schlocktoberfest 2005 has an array of buoys that, at full power, will detect fish clear across the planet, while boiling away the oceans on their side of the planet.
In this strip, Schlock tells us that the plasgun can be used to send 5mm blasts that can travel up a sniper's scope into his brain without scorching the furnishings. This came as news to everyone, given that, as Kevyn points out, Schlock has never willingly used any setting below "vaporise the target and set the room on fire".
Riff is, in general, a very enthusiastic supporter of this trope. Regard "party favors".
The Order of the Stick: Familicide. Nothing says "overkill" like making Black Dragons the newest member of the Endangered Species list. Just how far past the spell ended up that is a sobering reminder of just how badly people underestimate the concept of OVERKILL.
The Cloyster spell. It shields the surrounding area in a barrier that prevents most forms of teleportation, sending spells, and divinations from entering, though the spell's creator Dorukan allowed a loophole for summons so his girlfriend could visit. The spell's duration lasts one week per the caster's level, so an epic-level caster could be shielded for months at a time. And if someone left the Cloyster'd area, the effect would follow them as well.
The Last Days of FOXHOUND: Vulcan Raven's take on the matter: "Subtlety is a thing for philosophy, not combat. If you're going to kill someone, you might as well kill them a whole lot."
In Quentyn Quinn, Space Ranger, the Empire of the Seven Systems responded to the (admittedly rather brutal) slaughter of one of their colony ships by incinerating an entire solar system.
8-Bit Theater: Black Mage's preferred form of attack - he has been known to vaporize forests, and at one point destroyed a city by accident when demonstrating to its mayor how he would destroy the city if he didn't get what he wanted. He has refrained from using spells in battles where his life was at stake because he viewed anything that wasn't complete overkill a waste of his time.
"Don't say another goddamn word. Up until now, I've been polite. If you say anything else—word one—I will kill myself. And when my tainted spirit finds it's destination, I will topple the master of that dark place. From my throne, I will lash together a machine of bone and blood, fueled by my hatred for you this fear engine will bore a hole between this world and that one. When it begins, you will hear the sound of children screaming - as though coming from a great distance. A smoking orb of nothing will grow above your bed, and from it will emerge a thousand starving crows. As I slip through the widening maw in my new form, you will catch only a glimpse of my radiance before you are incinerated. Then, as tears of bubbling pitch stream down my face, my dark work will begin. I will open one of my six mouths, and I will sing the song that ends the Earth."
At the end of the Bloodsuckers Are Not Sexy arc of Fafnir The Dragon, Stephanie Meyer comes up with the brilliant idea of inventing time-traveling mermaids. The first one she runs into is... decidedly less than friendly.
A.R.I.E.L.: I am the Automated Response, Investigation and Extreme Liquidation unit, also known as A.R.I.E.L. In the future, you, Stephanie Meyer, will instigate Lack-of-Judgment Day, in which nearly every mythological creature is melted down into plastic goo and repackaged as teenaged heartthrobs. Meyer: Oh, that sounds romantic! (targeting computer currently highlighting Kill It with Fire) A.R.I.E.L.: On behalf of what few intelligent creatures remain... *opens fire* #$@% YOU!!!
Dating A Team Magma Grunt is a sequel to the events of Pokémon Ruby and Sapphire following Brendan and his relationship with a Magma Grunt. When the Grunt is insulted by a Team Aqua Grunt, Brendan challenges her to a Pokémon battle and promises to use a ground type against any of her water types on the condition that she apologies to his girlfriend if he wins. Sounds pretty tricky, right? Well it might've been had he not immediately whipped out a Master Ball. Cue Primal Groudon's Sunny Day and a brutally torn up area with its footprints embedded into the cement.
Land Reclamation in Stand Still, Stay Silent. How do you make certain you got rid of all the monsters in the area you intend to colonise? First, you send in scouts, to map out the area and get a feel for where the monsters might be lurking. Then you send in Hunters with high-powered rifles to deal with all the ambulatory monsters. Then come the Cleanser squads, who use fire and explosives to destroy anything and everything a monster might use as a nest (usually it involves leaving the area a charred wasteland). After that you wait for winter, so that any missed monsters freeze to death, along with The Virus that created them. Then you send in the hunters again, this time along with specially trained cats and their handlers, to track down anything you missed. THEN you set up a palisade or electric fence around the area, so no new nasties can get in. And the worst thing? By all accounts, this isn't overkill in any way.