Sometimes, it seems like all of the truly dramatic anime fights are down to the wire skirmishes where it's not clear until the very end who will win. While there's nothing inherently wrong with these close calls, no one wants to see the same kind of battle over and over again. Sometimes, what you want is to watch one person absolutely trounce their opponent because they're just that much more powerful.
One-sided anime fights appear in most shonen series, including One Piece, Naruto, My Hero Academia, Black Clover, and more. They also appear in most serious and disturbing shows like Berserk - and those scenes are a heck of a lot gorier. When the person curb-stomping their enemy is a hero, as is the case when Luffy takes out Bellamy with a single punch, it's an awesome moment that makes viewers cheer for the hero. When the one taking out their enemies with no effort is the villain, as is the case with Madara when he goes up against the Shinobi Alliance, it shows what kind of danger the heroes are up against.
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When Madara faces the Shinobi alliance - which consists of some of the strongest ninja in the known world, as well as thousands of competent soldiers - none of them stand a chance. He dismisses attacks that most would find fatal, blasts through scores of enemies within seconds, and generally commands so much power that Gaara wonders out loud if they are fighting someone with the power of a God.
As part of the exam he must pass to become an S-Class mage, Natsu faces off against Gildarts. Gildarts is so much stronger than Natsu that the reason he claimed to be "unprepared" for Natsu's attack was that he had to tone down his powers enough that he'd be able to avoid completely wrecking Natsu. Natsu is able to at least force Gildarts into activating his magic, but he still barely makes a dent in his defenses, and Gildarts' powers are obviously beyond anything that Natsu can handle, and he surrenders.
Luckily for him, giving up was exactly what he needed to do for Gildarts to pass him on to the next part of the exam. To Gildarts, what's important is not whether Natsu is strong enough to beat him - he knows he isn't. What's important is that he know his own limitations and make an appropriate decision based on those limits.
By the time Roy gets to Envy, the homunculus is already on the verge of being destroyed - Hawkeye has been shooting at them, and they're barely able to mount a defense. Despite this, Roy comes at them with full force, using his fire abilities to burn Envy to a crisp. Though Envy screams that Roy is a filthy human who shouldn't underestimate them, they're still defeated more or less immediately, This gives way to one of the saddest scenes in anime history - the one where Envy is reduced to a shriveled husk of their former self, begging for mercy and declaring their wish to have the same kinds of bonds and emotions that humans have.
At the end of Season 3, Class 1-2 meets The Big Three - seniors at their school who have distinguished themselves as some of the greatest in-training heroes that school has to offer. In order to demonstrate his abilities and give his juniors a challenge, Mirio Togata offers to fight the entire class. The only person who is able to make any headway whatsoever is Izuku - everyone else is defeated almost instantly, without being able to figure out anything about what his quirk might be. At the end of the fight which leaves the entire class defeated and exhausted, he explains that his quirk is Permeation, an ability that allows him to phase through matter at will.