"When a fight is just plain wrong!
—The Curbstomp Song
So, the new episode of your favorite show is on. Ooh, this is good. Emperor Evulz and Bob are finally meeting face to face and there's gonna be a fight. Evulz is pretty tough: he's the Big Bad, he's got lots of Spikes of Villainy, a big, nasty weapon, and he killed Bob's sister last season. Bob is looking pumped too: He's got a calm yet battle-ready demeanor, an Infinity+1 Sword, proper fighting attire, The Power of Friendship and a reason to fight. Everything looks evenly matched and set for a huge battle.
But in the immortal words of Pearl Forrester: ORRRRRR.... IS IT?!
Fast forward a week and you've got the next episode. Wait, something's wrong here. Bob is predicting Evulz's moves to the inch, hitting him with every move in his own arsenal, and not even getting tired whilst doing so! By the end of the episode, Evulz is stone dead, and Bob hasn't a drop of blood on him except for Evulz's. He wipes off the sword, sheathes it, says something about his sister, and walks into the sunset. Evulz has just been subjected to a Curb Stomp Battle.
As with all tropes, this can be done well or done poorly. A hero doing an epic ass-kicking to an overconfident, Smug Snake of a villain can be both incredibly awesome and cathartic, and an intelligently done one-sided battle can leave you as breathless as one that's close. And really, having it always looking like the villain is winning before the hero makes a comeback makes most fights incredibly predictable and the villain's early lead increasingly meaningless. On the villain side, this is an excellent way to establish someone as a threat, to put just that much more tension to the plot.
Be wary though, if, for example, both sides are known to be the best and/or the ass kicker seems to be pulling his skills out of nowhere. Expect cries of Mary Sue and The Worf Effect, with doses of Stuffed Into the Fridge and Faux Action Girl too if the victim is female. There's a fair chance that Unstoppable Rage is involved or the hero's Super-Powered Evil Side decided to rear its ugly head.
The name comes from the act of forcing someone to lie down in the street and bite the curb, then stomping on the back of their head. About as humiliating an ass-kicking as you could imagine, especially since it kills you.
Sometimes this is played for humor; other times, people try to use it as a Crowning Moment of Awesome for the hero. But it can still be annoying when done badly.
Sometimes it actually makes sense by the logic of the story, but writers use Third-Act Stupidity to avert it.
Sometimes, too, a battle logically should be a curbstomp, but isn't, and no real explanation is ever offered as to why the winner won. This can be, in its own way, just as dissatisfying as a curb stomp that makes no sense.
Compare Pendulum War, which is where sides take turns to perform this trope upon each other. For the Professional Wrestling equivalent, see Squash Match. In video games, see Flawless Victory. Breather Bosses and Anticlimax Bosses are the types most likely to be on the receiving end of a Curb Stomp Battle. If this is done to the heroes, on the other hand, it becomes a Hopeless Boss Fight, often from a Hero-Killer. Compare Won't Work On Me. Contrast Story-Breaker Team-Up. If the curbstompee manages to get a few good hits in to show that they're not totally helpless, it's a Curb Stomp Cushion.