Most characters play fair in anime, and follow the rules of the established combat system. This leads to balanced fights where everyone has a chance to win, and the characters must rely on creative thinking and resourceful tactics to be victorious. There will always be rule breakers, however, who simply deploy overpowered and unfair attacks or skills to easily win.
Plenty of villains resort to OP attacks. The most overpowered villain techniques and moves either break the rules of the combat system entirely, have no real countertechnique, or have so much offensive power that no one could hope to defend against them. Such techniques are risky to write, too, since they sometimes force authors to use cheats to bail the hero out. But when written well, OP villain attacks are fun to watch and raise the stakes like nothing else can.
10 Kaido's Dragon Breath Attacks (One Piece)
Some villain attacks may not have proper names, but they are still enormously powerful and easily recognizable. One example is Kaido's ability to perform devastating breath attacks in his dragon form in One Piece. Like most typical dragons, Kaido can breathe fire, to the point he can instantly wipe out a mountain and everything on it. That's far beyond what most One Piece villains can do.
Kaido isn't limited to fire, either. He can also create lightning and bladed air with his breath attack, making him more flexible in battle if an enemy can resist certain elements. On defense, Kaido can use his fire breath as a protective cloak, fending off physical attacks with extreme heat.
9 Kaguya Otsutsuki's Eighty Gods Vacuum Attack (Naruto)
Over time, Naruto kept upping the ante with ever-stronger ninjutsu and incredible feats of taijutsu, from Might Guy's inner Gates being released to Pain's Almighty Push to wipe out the entire Hidden Leaf Village. Characters like Pain and Madara Uchiha all felt OP, but then Kaguya Otsutsuki outdid them all.
As the mother of chakra, Kaguya was practically a deity, and she had OP techniques to match. Her Eighty Gods Vacuum Attack, when combined with Kaguya's Byakugan, could vaporize any enemy force with impunity, and easily destroy a Six Paths Chakra Susano'o as well. This attack is also too fast for any mortal ninja to escape, giving Kaguya another unfair advantage.
8 Overhaul Quirk (My Hero Academia)
The masked villain Overhaul wielded one of the series' most overpowered Quirks of all, simply named Overhaul. That Quirk allowed its wielder to reshape any matter with a touch, from healing his body to blasting someone apart to merging other bodies into his own to get even stronger. He could also form barriers and spikes from the terrain.
Only the power of One For All with Eri's support stood a chance against this limitless villain power and its ability to create or destroy anything. Not even Mirio Togata and Sir Nighteye stood a chance against the power of Overhaul, and neither would 99% of My Hero Academia's other heroes, either.
7 Aizen's Kyoka Suigetsu (Bleach)
Bleach features a variety of devastating villain techniques, from Ulquiorra's Cero Oscuras to Barragan's Respira and Zommari's ability to control people with his eyes alone. However, it's Sosuke Aizen who has the most unfair ability – to create convincing illusions with his shikai, Kyoka Suigetsu.
That ability is even stronger than it sounds. The hypnosis actually affects all five senses, not just sight, and the illusions may last for years or even decades if Aizen needs them to. There is also no limit to how many people Aizen can fool with his shikai, and the affected people almost never realize what's happening, either. His enemies might spend years living in an illusion while Aizen is free to do whatever he wishes to advance his conniving plans.
6 The Rumbling (Attack on Titan)
At first, Eren Yeager was a shonen anime hero in Attack on Titan, but all that changed when Eren learned of the outside world and the truth of the Eldian people. He became a radical and an Eldian nationalist of sorts, and seized whatever power he needed to take on the entire world for Eldia's sake.
Eren's endgame as a hero turned villain was to use the Founding Titan to begin the Rumbling. That apocalyptic technique involved Eren's giant Titan roving across the world, leading an army of countless Colossal Titans to trample absolutely everything underfoot until only Paradis Island itself remains. No Titan Shifter can resist power like that.
5 Time Freeze (JoJo's Bizarre Adventure)
Some Stands found in JoJo's Bizarre Adventure have rather niche and specific abilities, such as weighing people down with guilt or turning people magnetic if they touch a false electrical socket. Other Stands, such as The World, used simpler techniques to give their users an advantage.
The vampire DIO could make any battle a one-sided slaughter with The World's ability to freeze time for everyone except himself. That's how DIO killed Noriaki Kakyoin, and he would have killed Jotaro Kujo as well if Jotaro hadn't miraculously learned to use the time freeze ability for himself.
4 Bullet Projection (Chainsaw Man)
The off-screen character known as the Gun Devil has killed countless thousands of people with minimal effort, making it one of the deadliest and most feared devils in all of Chainsaw Man. Protagonist Denji the devil hunter is expected to fight that monster at some point, but he's not ready to face power of that caliber.
The Gun Devil can use a move called "Bullet Projection" to fire bullets at specific targets within one or more kilometers around it, and with perfect precision. No other devil can race across the landscape and slaughter thousands of people in mere seconds but the Gun Devil can, showing just how OP this monster really is.
3 Energy Projection (One-Punch Man)
The alien warlord Boros was already overpowered compared to the heroes of One-Punch Man in his default mode, but he could get even stronger to become a world-ending threat. Aside from techniques like flesh regeneration, Boros can use Energy Projection to devastate anything or anyone around him with devastating results.
Boros could use Energy Projection to destroy parts of a massive, highly durable spaceship, and when combined with Boros' punches, Energy Projection could wipe out entire cities at a time, a move practically no one else in One-Punch Man could ever achieve even if they wanted to.
2 The Death Note (Death Note)
In the Death Note universe, the notebooks were totally neutral in the sense that anyone could use them, hero, villain, or anything else. Still, anime fans may agree that there's nothing heroic about the notebooks' murderous power, and it's easy to abuse that power, as Mello did after L's death.
In Mello's hands, the Death Note became a grossly unfair advantage for him over Near and all his other enemies. It helped that Mello had the aid of Kal Snydar, who had acquired the Shinigami eyes to allow Mello to easily kill anyone he wanted. The only limitation, as Mello failed to learn, was that he couldn't use the Death Note to control someone and make them cause other deaths.
1 Infinity Big Bang Storm (Gurren Lagann)
The power scaling of Gurren Lagann is legendary. It's a mecha anime that keeps upping the ante with cartoonish enthusiasm, and anime fans can't get enough of it. The giant robots in the first story arc were already impressive, but the climactic final battle made both the heroes and villains overpowered on an incomprehensible scale.
Simon's own mech became larger than the universe itself, and the Antispiral responded in kind with his own Granzeboma. At one point, the Antispiral used the Infinity Big Bang Storm technique to slam two galaxies together and add his own energy, a technique whose power rivaled the Big Bang itself, hence its name. No other OP anime attack can compare to a cosmic assault like that.