When One-Punch Man hit the scene a few years ago, it completely flipped the superhero genre with a simple but genius premise: what if the hero is just way too strong? Saitama’s ridiculously overpowered abilities mean he can wipe out any villain with a single punch, making even the most intense battles feel anticlimactic. So, for creator ONE and illustrator Yusuke Murata, the challenge was: how do you build tension when your hero can end every fight instantly?
The answer lies in crafting villains so outrageous and powerful that even though we know Saitama will ultimately win, we can’t help but be amazed by their strength. However, not every villain in One-Punch Man has the same level of power, and some stand out way above the rest in terms of strength and the chaos they unleash. So without further ado, here are the top 10 most powerful One-Punch Man villains who dared to challenge Saitama and made us believe they could actually be a threat.
10) The Deep Sea King
The Deep Sea King is the main antagonist of the Sea Monster Arc and a straight-up nightmare. After his underwater minions failed, this ruthless Seafolk ruler emerged from the ocean depths to finish the job himself. He saw humans as nothing but prey, and in his eyes, he was the ultimate being destined to rule Earth.
What really made the Deep Sea King terrifying wasn’t just his incredible power, but his sadistic nature, which is genuinely disturbing. We watch him transform into a much stronger version of himself when he’s properly hydrated by rain, which boosts his already devastating strength to insane levels. He defeated multiple A-Class and even S-Class heroes, including Puri-Puri Prisoner, and almost killed Genos, before Saitama arrived to end his reign of terror.
9) Overgrown Rover
Picture the biggest, scariest dog you’ve ever seen, then multiply that by a hundred. That’s Overgrown Rover, a terrifying giant black beast with six glowing red eyes that will genuinely haunt your nightmares. It looks like someone took a regular dog, fed it pure evil, and let it grow into a nightmare with fangs that could cut steel.
Rover can fire energy blasts from its mouth that turn other monsters into ash in seconds, wipe out entire city blocks, and make the ground shake like an earthquake. And if that’s not enough, it’s fast as lightning, too, running up walls like gravity doesn’t exist and sneaking up on heroes who never see it coming. Even when top fighters like Bang and Bomb teamed up against it, Rover just shrugged off their best attacks like they were playing fetch.
8) Black Sperm
Black Sperm made his first appearance during the Monster Association arc as one of the most dangerous villains One-Punch Man fans had ever seen. He belongs to an unknown race and serves as a Dragon-level executive member of the Monster Association, which makes him a serious threat even to S-class heroes. Despite his small, twisted black humanoid appearance, we learn that Black Sperm is far from weak and has enough power to crush some of the series’ strongest fighters.
With his unique ability to merge countless cells together, he can create forms that can take down heroes who previously seemed unbeatable. His two most feared transformations are Golden Sperm, made from 43 trillion cells, and Platinum Sperm, formed from nearly 54 trillion cells. When Black Sperm reaches his Platinum form, he becomes so strong that only a handful of S-rank heroes could even dream of surviving a fight against him.
7) Fuhrer Ugly
Fuhrer Ugly is tall and obese with grotesque facial features and stands as one of the Monster Association’s most terrifying executives. He’s driven by pure hatred for anything he considers beautiful, his twisted obsession with ugliness and resentment towards beauty making him one of the most psychologically disturbing monsters in the series. This villain proved his power when he completely destroyed the number one ranked A-Class hero Sweet Mask, making it look absolutely effortless.
After being partially digested by fellow monster Gums, Fuhrer Ugly gained a massive power upgrade that gave him deadly acid abilities. These new acid powers could burn through even S-Class hero Blackluster’s tough skin, showing just how dangerous he had become. The monster even managed to kill members of the Swordmasters’ Council before finally meeting his end when Garou kicked a massive hole straight through his chest.
6) Evil Ocean Water and Sage Centipede
The Sage Centipede and Evil Ocean Water were sent by God to destroy the heroes and are two of the most terrifying monsters ever seen in One-Punch Man. Centisennin or Sage Centipede was a centipede monster that was far, far more massive than the Elder Centipede seen in season 2, emerging from underground where it had been recovering from a brutal fight with Blast. It had 6,666 limbs and was so tall that its head was nearly outside the atmosphere.
Evil Ocean Water was one of the most bizarre yet deadly monsters in the series, starting as Evil Natural Water before it evolved. When it made its way out to sea and became Evil Ocean Water, it could project beams of water at intensely high pressure and create massive tidal waves that could wipe out entire cities. If Saitama and Garou hadn’t shown up to stop them, these two monsters would have likely destroyed everything and everyone.
5) Psychos-orochi Fusion
While Psykos and Orochi are two different characters, they combine to form an incredibly powerful being that’s one of the most terrifying threats in One-Punch Man. On his own, Orochi was already a dragon-level threat, and one of the strongest monsters on the planet. Psykos wasn’t as skilled individually, but once Orochi combined with her, the fusion became so powerful that one of their attacks managed to slice the Earth’s surface.
In order to beat this terrifying fusion, we watch multiple S-rank heroes work together in an epic battle. Once the fusion took too much damage, Psykos decided to split away from Orochi and escape. While Orochi was completely destroyed as Tatsumaki delivered the final blow.
4) wasteful
The main antagonist of the Alien Conquerors arc, Boros is easily one of the most memorable villains in One-Punch Man. After destroying countless planets across the universe, this alien warlord and his Dark Matter Thieves finally arrive on Earth looking for the ultimate fight. For years, Boros had been searching for someone who could actually challenge him in battle, and Earth seemed like his last hope.
Boros’ incredible array of powers put him leagues above other monsters. He could create devastating shockwave attacks and move at incredible speeds while his insane regeneration abilities let him recover from almost any damage instantly. Even more impressively, Boros was actually able to survive multiple hits from Saitama and even managed to kick our bald hero all the way to the moon.
3) Empty Void
Void is an unfortunate figure in One-Punch Man as, before the recent retcons, he had an incredible visual showcase for his abilities and was truly poised to be a menace in the series. His former partnership with Blast, and maliciously twisted dimensional-scale abilities empowered by a certain enigmatic deity, made him an existential threat to the world in the Neo Heroes Saga’s Ninjas Arc. However, even with the ability to carve through all reality of a given dimension with the aptly-named “Dimension Slash”, Void still falls short of becoming a serious threat, albeit in an extremely funny way you must see to believe, as it broke the OPM fandom when it happened.
Void’s position as a villain drew increasing doubts with the latest retcon, but his abilities were nothing to scoff at. Were it not for Blast, his Dimension Slash would have destroyed the entire Hero Association headquarters. However, while his abilities themselves are likely among the strongest Saitama has ever witnessed, he put up a comically short fight against our hero before the latest redraw in 2025.
2) Garou
Garou stands as the ultimate adversary in One-Punch Mana monster who pushed Saitama harder than any other enemy we had witnessed before him. While Boros amazed fans with his incredible strength, Cosmic Garou completely overshadowed him by actually forcing Saitama to fight seriously for the first time. We also get to see their battle literally destroy chunks of Jupiter and nearly wipe out all life on Earth.
What makes Garou truly special is his ability to copy and evolve during fights, turning every technique used against him into his own weapon. We follow his journey as he masters martial arts under Silver Fang before becoming the feared “Hero Hunter,” but his real transformation began when God granted him cosmic powers. Garou became the only villain to truly anger Saitama after killing Genos, proving that this monster could achieve what no other enemy had done: making our bald protagonist lose his cool and fight with genuine desperation.
1) God
God is a mysterious and elusive figure in One-Punch Man whose powers have yet to be fully understood, yet it’s through its continuous involvement in the plot, from murals to its meddling in the Monster Association Arc, that fans understand its position as the most nefarious villain yet. God has granted the previous strongest characters, Garou and Empty Void, immense powers suited to their skillsets, and is able to show immense influence over others through its Mysterious Cube artifacts; while its influence on Saitama seems to be nullified, its empowerment of Garou is the only thing to truly prompt Saitama to go to his most serious extremes.
In a move emulating the tropes of JRPGs everywhere, the only true ultimate opponent for Saitama is inevitably God itself, forgoing all pretenses. We don’t know just how powerful God is, but given the dimensional seal keeping it in place, and numerous near-misses, the series is clearly gearing up for Saitama’s great challenge and ultimate foe, at least other than King in a fighting game tournament, is none other than God itself. With speculation that the latest redraws and retcons are a meta version of Murata spelling out that God is changing the timelines, it’s suspected that the strange mass of brain cells is more powerful than we’ve yet to imagine.
