In the backstory of the game Fading Suns, the meeting between the Vau and the Second Republic (nearly at the highest point of its power and technological advancement) is the conquest of a (unknown to the humans) Vau protectorate. A few days later, a Vau ship appears, destroy every trace of human presence in a matter of minutes, and leaves a message not to fuck with this star system. Of course, humans being what they are, assemble a combat fleet to attack the planet the Vau vessel came from. The only ship to come back had been spared to serve as a warning to the Second Republic.
In the backstory of Planescape, it's mentioned that Sigil's mysterious ruler/protector/overlord, The Lady of Pain, has killed gods in her time...and the confrontations were not the usual, cataclysmic, ground shaking clash of the titans one would expect from a duel between major powers. They were much more of the "angry Lady = dead schmuck" variety. The only entity that has ever so much as slowed her down is Vecna, a millennia old liche and greater god, who was in the process of reshaping the multiverse at the time. Everyone else just dies.
It should be noted that said battle with Vecna is subject to Fanon Discontinuity by many Planescape fans.
She can appear in Planescape: Torment as a non-standard game over if you cause enough trouble in her city, perma-killing the Nameless One in one shot.
In Exalted, this is almost guaranteed to happen any time a Celestial Exalt goes in against mortals, or even Terrestrial Exalted. It's even possible to curb stomp gods if you have the right build.
'The right build', of course, meaning 'being anything stronger than a regular heroic mortal'. And even then, a heroic mortal with an artifact that allows him to hit dematerialised spirits...
Depends on the god. Lesser river god? Fuck, yeah. One of the higher-ups, i.e. The God of Southern War and Cattle, or the Celestial Incarnae? Not so much.
The card Crushing Attack in Legend of the Five Rings can only be played during a battle if you have more than double the strength of the opposing army. It immediately ends the battle, preventing any actions from your opponent that might have swayed the outcome, purely by overwhelming might.
High-level characters in Dungeons & Dragons can typically be counted on to wipe the floor with low-level characters in a straight-up fight. This is especially true if spellcasters are involved, as many high-level spellcasters have spells that can instakill characters below a certain HD level with no saving throw.
Spycraft, and later D&D 4th edition, had separate NPC types for "minions" or "standard" characters and "special characters". The latter have hit points like the player characters, but the former die with a single successful attack. Needless to say, a combat encounter designed primarily around standard/minion characters tends to be this until players reach the 'boss'.
Normally what happens when a Planetary Defence Force goes up against anybody. Think the Imperial Guard, except they lack the one thing that make the Guard a force to be reckoned with: sheer quantity. Happens depressingly often with the Imperial Guard as well, especially in stories where the protagonists areSpace Marines. When Tyranids appear in fluff, they're usually the ones delivering the curb-stomp.
Horus vs. Ollanius Pius. The former was the strongest and most skilled of a bunch of demi-gods before the Chaos Gods used him as a receptacle for power. The latter was a standard Guardsman, the same as the ones who die in droves against the alien and mutant every day. It could've only ended one way, but Pius died standing.
Primarch Sanguinius vs. Ka'Bhanda. After a short battle, the greatest of Khorne's daemon lords was sent back to the Warp with no wings, a broken back and a serious case of butthurt.
The Battle of the Blood Nebula. The Imperium, finally having enough of the Eldar, decides to root them out at the source and destroy a Craftworld. Unfortunately, the one they chose was Biel-tan. Result: an entire Imperial sector fleet annihilated, with Biel-tan taking minimal loss. The defeat was so utterly crushing that it caused the Imperium to drop the whole "exterminate the Eldar" idea and simply deal with them as they crop up, although it didn't stop the Invaders Space Marines from delivering their own curb-stomp on Craftworld Idrahae later. In a three-fer stomping, the survivors of Idrahae went to Craftworld Alaitoc for help, and Alaitoc sent a force to the Invaders' homeworld; there are only 12 Invaders marines left now.
The Doom of Malan'tai. An entire Eldar Craftworld lost to a lone Tyranid zoanthrope. Ok, admittedly, the stomping happened after it ate all of the soul energy of the Craftworld's Infinity Circuit, but still, not one of the Eldar's finer moments.
Another Eldar curbstomp: when Slaanesh was born, S/He ripped through the Eldar pantheon and everyone except Isha and Cegorach died horribly in an act of supreme deicide. Even Khaine the Bloody Handed got has ass handed to him.