Main Characters | Hero Association (S-Class Heroes) | Neo Heroes | Villains and Monsters (Monster Association) | Others
Voiced by: Yūki Kaji (Japanese), Erik Kimerer (English), Rick Loera (Latin American Spanish)
A ninja with superhuman speed who works as a freelance assassin. After a humiliating defeat by Saitama, Sonic declares himself his unofficial nemesis and hounds him for the opportunity to claim his revenge.
- Affably Evil: In the third OVA when he gets A Day in the Limelight. When he's off the job he's an all-around decent guy.
- Amusing Injuries: The first time he fights Saitama, he's defeated via a Groin Attack. In their second fight Saitama smashes his face into the ground so hard that in the extra page it's shown that it left an imprint in the concrete. In a special chapter, later on, Saitama defeats him with another Groin Attack, this time accidentally elbowing him in the groin.
- Anti-Villain: Primarily an antagonist but he's just as likely to fight a human villain or a mysterious being if it serves his best interests. More so in the third OVA where he's portrayed sympathetically and aptly described as "complicated".
- Assassin Outclassin': He's a Professional Killer, and his primary target is Saitama. While he was never actually hired to kill Saitama, in their first encounter Sonic mistook him for a Paradiser, who he was tasked with disposing of.
- Ax-Crazy: At times. When Sonic recognizes an opponent as his rival, he does whatever he can to initiate the battle, such as causing massive property damage and endangering the surrounding citizens in order to get Saitama to fight him.
- Back-to-Back Badasses: With Flashy Flash, when a group of ninja graduates gangs upon them. They were classmates once and sparred together, so their teamwork is flawless despite the years of separation and they dispatch the ninjas without much difficulty.
- Bishōnen: Sonic is a slim young man with a feminine face, long black hair tied up in a topknot, and large grey eyes.
- Blood Knight: He's positively thrilled when he comes across an opponent who can actually be a challenge; he immediately realizes that Saitama isn't his target, but doesn't care as long as he gets to fight someone that powerful.
- Butt-Monkey: Nothing ever goes right for him.
- Card-Carrying Villain: Declares himself as one during his second encounter with Saitama in order to goad the latter into fighting him. This works much better than expected, as Saitama was in the middle of searching for a villain to defeat in order to prevent him from losing his hero status due to inactivity.
- The Chew Toy: A Running Gag for Sonic is that with every confrontation with Saitama, he is beaten in a humiliating way. First time was being punched in the groin, second time was being karate chopped on the head from behind and slamming into the concrete making a mark where he landed, the third time saw his ultimate technique completely outclassed by Saitama's Serious Side-To-Side Jumps, the fourth time (in a special chapter) Saitama elbowed him in the groin while his vision was impaired and the fifth time he stepped in some dog poop, causing him to slip and get hit by his own exploding shuriken.
- Close-Call Haircut: During his fight with Genos, Sonic's hair was cut short by the former. It also counts as a Traumatic Haircut, as said haircut pissed him off.
- Clothing Damage: Gets his clothes torn in almost every fight he's in.
- Curb-Stomp Battle: No points for guessing who wins in his fights against Saitama.
- Dark and Troubled Past: Sonic originated from the Ninja village, a hellish place where orphans were trained to become efficient killing tools. A "day" there consists of 72 hours with only 6 to sleep, food are deliberately made tasteless, outside contacts are cut off, communication is prohibited, and all the trainees are drugged so that they can't kill themselves. Despite all this, young Sonic managed to hold onto humanity, secretly befriended Flashy Flash and told Flash about his dream to abolish the system and rehabilitate his peers for a better life. However Flash believed they couldn't be saved by anything but death and betrayed the plan at the last moment. Flash attempted to mercy kill Sonic by poisoning him the night before, then proceeded to slaughter everyone at the graduation exam. Sonic didn't die from the poison due to his strong immune system and ended up being sole survivor of the class.
- A Day in the Limelight: The third OVA is centered around his training after Saitama defeats him for the first time.
- Deliberate Under-Performance: Sonic's Training from Hell punished the weakest students by submitting to the harshest training. However, he reveals to Flashy Flash that he deliberately slacked off in order to get a more challenging training and was kind enough to look out for him. Ironically, Flashy Flash had been doing the same.
- Department of Redundancy Department: His name. Lampshaded by Genos. It later turns out that this is the standard naming procedure in the Village.
- Determinator: The man simply will not give up on his quest to defeat Saitama. He knows when to quit and come back later, but that's about it. He is even willing to transform himself into a monster by eating a Monster Cell if meant gaining more power to beat Saitama. Unfortunately for him, Gale Wind and Hellfire Flame fail to mention that he needed to eat the Monster Cell raw, but since Sonic cooked it, the Monster Cell was rendered inactive and he only got an upset stomach.
- Exposed to the Elements: Sonic slips out of his clothes to escape the Deep Sea King's grasp. Being exposed to the rain in this state doesn't appear to bother him in the slightest.
- Flash Step: He can do this thanks to his super speed.
- Fragile Speedster: He's incredibly fast, but his physical strength leaves something to be desired. He usually compensates by using ninja weaponry and attacking the enemy's weak spots like the face or neck, but sometimes that's still not enough. In his duels against the Sea King and Genos, Sonic runs circles around his opponent, but he just can't hit hard enough to deal even Scratch Damage, which speaks volumes since Genos is a Glass Cannon who tends to lose his limbs when he gets hit. He possibly gets over this later when he managed to tank Brawny Muscle's attack, the ninja known as physically strongest, unscathed and kill him with only a single elbow.
- Full-Frontal Assault: Being forced to take off his clothes to escape a monster doesn't seem to faze him. Genos thinks he's weird.
- Giving Them the Strip: When the Sea King tries to crush him in his fist, he abandons all of his clothes in a last ditch effort to escape.
- Groin Attack: Accidentally runs his crotch directly into Saitama's fist in their first encounter. In the anime, they break out a We Are Experiencing Technical Difficulties card to cover his horrific scream.
- Highly Visible Ninja: While he is capable of stealth, he always announces his presence to his opponents, particularly to Saitama. He gets away with it because he's fast enough that he can kill most enemies before they realize what's happening.
- Jade-Colored Glasses: There was a time when Sonic was actually a relatively kind boy. He partnered with Flashy Flash and was kind enough to help the seemingly weaker student, and also dreamt of destroying the ninja village and free the orphans. Flashy Flash did that for him while he was sick and since then he's become a mere mercenary looking to get stronger.
- Jerk with a Heart of Gold: In the third OVA, he helps a baby boar by killing a giant snake that tries to eat it and befriends an old man named Frank. He even goes and names the baby boar "Ino", spends the rest of the episode with it in his training, and gives some advice to Frank to help the old man defeat his arch-enemy.
- Long-Haired Pretty Boy: Until his hair was cut short, but remains a bishie.
- Mr. Fanservice: Murata puts a lot of effort into showing just how tight his suit is.
- Mythology Gag: As a side note, this character also appears in one of ONE's other series, Makai No Ossan (Old Man Of The Underworld), as a flasher who startles people at random in school. This joke is referenced during Genos' first encounter with Sonic during the Sea King story arc.
- Ninja: Of course! He was raised as one. As an experienced ninja, it can be assumed that Sonic is a master of ninjutsu and has knowledge of various deadly techniques. He's displayed multiple techniques involving his incredible speed and weapons.
- Off with His Head!: How he deals with anyone he attacks.
- Overshadowed by Awesome: The series makes it clear that, despite his obsession with the nigh-unbeatable Saitama, Sonic is possibly one of the most dangerous human characters in the series, to the point Fubuki herself notes that he could easily be on par with S-Class heroes if he ever tried. He just picked the exact wrong person to see as a rival. Notably, his power and speed, after much training throughout the series is shown to be on equal footing with a casual Flashy Flash, his friend and rival from the Ninja Village and an S-Class Hero in his own right.
- The Rival: Sonic is Saitama's self-proclaimed rival and recurring enemy, even though Saitama is way above his weight class. He has a more traditional and balanced rivalry with Flashy Flash, who underwent the same hellish training in the Ninja Village Sonic did.
- Scarf Of Ass Kicking: Until his fight with Genos.
- Slasher Smile: He gets a "child-like smile" on his face when he faces a strong opponent like Saitama. He describes it as a bad habit.
- Smug Super: He will always boast about how untouchable he is because of his Super Speed to his opponents.
- Stalker Without a Crush: Becomes obsessed with defeating Saitama after being curbstomped by him twice. In his own words, he can't overcome the feeling of being a loser unless he beats Saitama. Unfortunately for him...
- Stock Shōnen Rival: He's probably the closest Saitama gets to one, though much like the satirical nature of the series he also has deconstructed traits. Like most rivals, Sonic views Saitama as a Worthy Opponent and is obsessed with defeating him, while also being a Smug Super in his own right. Unlike most rivals, he's for the most an Unknown Rival to Saitama, who doesn't even consider Sonic worth his time. In addition, the power gap between him and Saitama (like most characters) is phenomenal and Sonic never remotely comes close to closing the gap. Though Saitama does keep letting Sonic go in the hopes that Sonic can grow stronger and one day pose a threat to him.
- Super Speed: Sonic's main ability is his extreme speed. He has been shown to be capable of dodging rocks and trees thrown at him with incredible force. How Sonic obtained his ability is unknown, but so far only Saitama and the monsterized ninjas have been able to keep up with him.
- Time to Unlock More True Potential: You've got to hand it to him, he trains really hard to try and give Saitama a challenge. Not that it helps, mind, but still he goes off to train and get more abilities after almost every defeat. And then when he decides Hard Work Hardly Works and to just eat a Monster Cell? He cooks it first thinking it'd just be common sense, and winds up just having really bad diarrhea instead.
- Unknown Rival: Although he declares himself to be Saitama's rival, the difference in strength is obvious and Saitama even has a difficult time remembering his name (he calls him "Cross of Bones Panic"). Sonic's persistence and constant attacks on Saitama eventually payed off as Saitama is capable of remembering his name in the Blizzard Group arc.
- Used to Be a Sweet Kid: He hated how the Ninja Village was turning kids into brutal killers and wanted to work with Flashy Flash to bring them down from the inside. But after Flash killed all the staff by himself, Sonic went on to become a criminal anyway.
- Villain Respect: While Sonic can't stand the fact that he keeps losing to Saitama and trains hard to defeat him, Sonic is one of the few individuals that takes Saitama and his power seriously.
- Vocal Dissonance: Virtually the only way someone can tell his gender without being told is his surprisingly deep voice. Downplayed a bit in the Latin American Spanish dub, since he speaks with a somewhat effeminate tone, except when he's screaming.
- When He Smiles: Not his slasher one. The OVA shows him smiling and it is pretty nice.
- Wild Card: Due to being an assassin for hire and having no status as a member of the Hero Association.
- Worf Had the Flu: His fight with Sea King; he's unarmed, having just broken out of prison, and while even a fully powered Sea King still can't match Sonic in speed, Sonic can't land any blows powerful enough to hurt him. Sonic runs away, and after arming up comes back, but by then Sea King's pissed off Saitama. According to Word of God, if Sonic had a weapon, he would have defeated Sea King in his base form.
- Worthy Opponent: He sees Saitama as this and won't rest until he defeats Saitama. On the flip side, while Saitama doesn't see Speed-o'-sound Sonic as a threat, he keeps letting him go so that Sonic can grow stronger and maybe pose something of a challenge next time. This is even lampshaded in the third special comic chapter "Catch and Smash". Later on, Flashy Flash notes that Saitama actually refers to Sonic by name, which is a level of recognition Saitama doesn't give to most people.
"Hero Hunter" Garou
Voiced by: Hikaru Midorikawa (Japanese), Greg Chun (English)
Debut: Chapter 45 (Webcomic), Chapter 39 (Manga), Episode 13 (Anime)
Disaster Level: Dragon, Above Dragon (Awakened)
- Adaptational Attractiveness: His webcomic incarnation looks more like a simple thug; Murata drew him as an athletic handsome dude wearing tight-fitting clothing.
- Anti-Villain: He may be playing for the monster's side but as it turns out he never really killed any heroes and doesn't even target civilians. Hell, he actually killed quite a few members of the Monster Association. The main reason he attacks the heroes is that he wants to destroy the status quo and get back at the popular people of the world. In the Manga, his goal is to, more or less, pull an Ozymandias from Watchmen where the entire world bands unite against him out of sheer terror.
- Armor-Piercing Question: At the end of his big Motive Rant, Garou attempts to hit Saitama with one of these, but it doesn't work. Saitama ends up hitting Garou with an Armor-Piercing Question of his own combined with a Kirk Summation, which causes Garou's determination to crumble instead.Awakened Garou: If you weren't here, I would have become the world's absolute evil. Unbiased terror scattered throughout the world...that can establish real peace. Don't think that all children are waiting for heroes. There are even kids around the world waiting for a great monster to take the stage. Can you save them!? Can you follow the ugly kid being picked on in the park!? I can! I can save the whole world with terror! While humanity is fearing Garou the Monster, everyone's hearts will unite to survive. Is there any peace other than this!? Can you create peace? Can you unbiased save the world with that flimsy cape? Do you have the means to stop the unseen tragedies? You're strong but so what? You may defeat me, but can you handle it?! THE RESPONSIBILITY!!! WELL!? IF YOU'RE GOING TO DEFEAT ME, THEN ANSWER THE QUESTION! WHAT WILL YOU ACCOMPLISH? Why will you kill me now? Do you have a sense of duty like mine? WHY...ARE YOU...A HERO?!
Saitama: It's a hobby.
- Arrogant Kung-Fu Guy: Used to be Bang's top student, before Bang found out Garou wanted to be a Monster. Garou is still quite confident of his skills, and pushes his limits daily. This backfires because Bang gets worried Garou might become an unstoppable monster, so he calls his brother, Bomb, for backup and they kick Garou's ass straight to the monster hospital. Yes, the monsters have a infirmary for monsters that get beat up by heroes and survive.
- As Long as There is Evil: Played With — Ultimately, Garou wants to be the "world-destroying evil" simply because at least against him humanity would stand a chance, because they could stand up against him as many times as it took to beat him. And by focusing on him, humanity would never have to worry about its greatest enemy: Itself.
- Awesomeness by Analysis: Garou is not only very skilled at fighting, he's also able to figure out the weaknesses of his opponent's fighting style through simple observation alone. Opponents may get some hits in at first, but once Garou figures out the technique, he will be able to counter anything that the opponent uses. He also does research on his targets to be able to better prepare himself for their inevitable meeting.
- Bare-Handed Blade Block: A more realistic version against Spring Mustachio and Royal Ripper, as he lets them hit one hand to immobilize them, and then beats them up with the other. He plays it straight against Atomic Samurai as Awakened Garou, as he catches the blade between two of his fingers, snaps it off, and then beats him up in the time it takes for Atomic Samurai to finish swinging his sword.
- Berserk Button: Absolutely DO NOT be a condescending jerk about justice and heroism in Garou's presence unless you want the most humiliating beatdown of your life. This happens with Superalloy Darkshine, who compared Garou's quest to a child playing monster, and with Sweet Mask when he tries to give a lecture on how pathetic the S-Ranks were being mid-battle. Garou responds by literally punching his face in, mid-rant.
- Big Eater: In Chapter 134, Garou ordered all the meats and salads on the menu at a restaurant and was able to eat the entire serving before attempting a dine and dash. Granted, before that the guy was unable to get a decent meal for at least over a day.
- Big Bad: The first true overarching villain the series has ever had, and genuinely retained this for a time.
- Big Bad Ensemble: He is this with Orochi in the Human Monster Saga.
- Big Red Devil: His Awakened appearance plays with it. His horns used to be his hair before he gained the desire to become a real monster for heroes to fight. This does two things: it changed his physical appearance to one similar to a demon, and all his hair turns into his two "horns", leaving him bald.
- Blood Knight: Garou truly enjoys fighting. Such as when he actively goes out of his way to hunt heroes in the name of his code and has a blast when doing it. He even has enough courage to challenge S-Class Heroes as they are probably the biggest challenge he'll get throughout his hunting spree. It is also expressed when he wears a truly arrogant grin on his face while he demolishes any one of them in his path.
- Broken Ace: Garou is a good looking guy, charismatic and an amazing fighter, that ultimately becomes so strong, only Saitama can beat him. But he also suffers from a plethora of deep-seated psychological issues that make him a very troubled young man.
- Bullet Catch: Up to Eleven, when he deflects all of Death Gatling's bullets fired in one explosive burst. He boasts afterwards that guns can no longer hurt him.
- Butt-Monkey: When Garou starts his crusade against heroes in the manga, he's just as likely to get his ass kicked as he is to kick ass. Against Watchdog Man for instance, he gets utterly outclassed and has to retreat, only escaping worse punishment because Watchdog Man doesn't venture outside his own territory. And every time Garou runs into Saitama, he gets knocked out instantly, with Saitama never even realizing who he punched out. One time Saitama even wonders right afterwards about that Hero Hunter he had heard about and whether he'd possibly be a challenge seconds after punching Garou through a wall. Overall, Garou has been knocked out thrice by Saitama before their ultimate confrontation.
- Card-Carrying Villain: He has "Hero Hunter" as a title. He introduces himself by walking into a meeting at the Hero Association, which is full of various rogues and evil doers. (in-context: The association was putting the word out about the world-ending prediction, hoping the Underworld might decide the world ending is against their own self-interests), and loudly proclaiming they are all weaklings and that he, the Human Monster, could defeat all of them right here to prove it... and then he actually does it. He then goes for a casual stroll while making a threat to the Hero Association head. He also doesn't pay for his meals.
- Came Back Strong: One of his abilities seems to imply "what doesn't kill me, only makes me stronger." This especially comes into effect in the latter part of the human Monster saga, when he begins fighting the merciless members of the Monster Association such as Royal Ripper and Bug God, Overgrown Rover, and Orochi, and begins growing exponentially because of it. This is part of Psykos's theory on breaking the limiter; by being exposed to near-death situations and then overcoming it, one can gain explosive bursts of power. Psykos engineered these situations in hopes of creating a being even more powerful than Orochi as her ultimate trump card.
- Chekhov's Gunman: He is mentioned in passing as the student who Bang beat up and expelled due to going wild and beating up all of the other students in Bang's dojo. He shows up several chapters later as a villain.
- Clipped-Wing Angel: When all of his areas of expertise are trumped by just how horribly unfair Saitama's strength is, Garou gradually becomes more and more of a literal monster. However, all this does is make him bulkier and easier to hit, though this makes him durable enough to tank Saitamas normal punches.
- Curb-Stomp Battle: Both played seriously and played for laughs — played seriously in that Garou is really brutal in beating up heroes, then played for laughs when Saitama lightly taps him for Dine-and-Dashing, which results in a OHKO. Ditto when Saitama mistakes him for a mugger while he's out wig shopping.
- His ultimate fight with Saitama is inevitably this. Even after evolving over 4 times into his "unfair evil" ultimate mode, he's unable to hurt Saitama. Despite this, it is one of the few fights that subverts the titular One-Hit KO rule, even getting Saitama to pull out his "Serious Series" moves to incapacitate him.
- Deliberate Injury Gambit: Several times Garou takes advantage of his Determinator Healing Factor to tank an attack in such a way it allows him to get in close and punish his opponent several times over what he got, such as when he impales his hand on Spring Mustachio's Finishing Move in order to take him out with one good strike.
- Deconstructed Character Archetype: Of Balance Between Good and Evil and As Long as There is Evil. Garou represents the idea that as long as good and evil both exist in the world, there needs to be a "balance" between them. As long as evil exists in the world, there needs to be good as well, and the only way that an absolute good can exist is for an absolute evil to simultaneously exist. The deconstruction comes into play when it's revealed that Garou isn't really evil at heart. He has a body count of zero and actively avoids harming innocent people, and takes mercy on kids such as Tareo and Zenko multiple times. Garou doesn't really want to do evil things, but rather wants to become the ultimate antagonist in order to force the world to focus on him and become better people that way. He believes there's too much picking on the little guys, and wants people to focus on a real threat instead of the kid who doesn't fit in, for example. Saitama slowly challenges his worldview by bringing up the fact that he's a good person who basically went with a half-hearted monster hobby because he lacked the conviction to be a hero, to be the change he really wanted to see in the world. In the end, Saitama asks him if he's okay with being a villain - Garou's facial expression very clearly says he isn't.
- Determinator: Even beaten, tired, wounded and poisoned, he never gives up and stops fighting. Until Saitama puts out the contradictions in his philosophy.
- It's also deconstructed because he isn't enough of a determinator. Despite never stopping in fighting, he became a monster as a compromise. His heart isn't in it, and he can never let go of his humanity and become a real monster. His real goal was to be a hero, but he lacked the conviction to follow through and according to Saitama, it's because he lacks confidence.
- Even Evil Has Standards:
- Garou isn't interested in killing civilians like "some sort of crazed mass murderer" - he's only a villain to fight heroes - and still takes time to help Tareo with his bully problems. When Tareo gets kidnapped by the Monster Association, Garou even saves him from their dungeon (though he is very Tsundere about it, and the two get split up before Tareo can actually reach safety).
- In fact, "bullying the weak" in general seems to be a weak spot for him. During his fight with Superalloy Darkshine, he starts curbstomping him so much that Darkshine loses his confidence and starts flashing back to when he was bullied as a kid. Garou actually stops mid-attack because he felt that something was wrong.
- He seems to subvert this when he threatens to kill Tareo, but this turns out to be a bluff, as Saitama points out.
- Garou isn't interested in killing civilians like "some sort of crazed mass murderer" - he's only a villain to fight heroes - and still takes time to help Tareo with his bully problems. When Tareo gets kidnapped by the Monster Association, Garou even saves him from their dungeon (though he is very Tsundere about it, and the two get split up before Tareo can actually reach safety).
- Evil Is Easy: According to Saitama, this is why he actually became a Noble Demon. To Garou, it was easier trying to bring world peace by being an all-powerful evil monster, because all he had to do was beat heroes. As Saitama observed, Garou chose this route because he did not have the confidence in himself to actually be The Paragon that he believed other heroes should be like. It's also deconstructed, since despite his noble goal, the truth is that by trying to be evil, he's really just half-assing it and against someone like Saitama, who puts all of his conviction in it, he will never win. Evil may be easy, but that doesn't mean you'll end up achieving what you really want.
- Expository Hairstyle Change: The aftermath of his battle against Saitama left him with shorter hair, as if to symbolize the removal of his previous Horned Hairdo and his desire to be a monster. He keeps this shorter hair as he continues to train in isolation afterwards. This hair also resembles his hairstyle as a kid, seen in flashbacks, showing a return to his true self.
- The Faceless: As Awakened Garou - although you see a few features, eventually he gets so strong due to Saitama getting serious on him, almost everything about him is blacked out and featureless - you can't even tell WHAT he looks like anymore. And then Saitama literally punches his face off, revealing his human eyes underneath.
- Fatal Flaw: In a roundabout way, Sloth. Garou desires to be the ultimate monster, noting that in doing so, humanity would unite against him rather tha pick on each other. However, despite his massive growing power, he doesn't really kill any of the heroes and ends up befriending a couple of kids. However, where this truly comes into play is when he faces Saitama. Garou puts up a good fight, but is still easily beaten by Saitama and Saitama realizes the truth through Garou's ranting: that Garou actually wanted to be a hero. However, Garou chose being a monster for his goal because it was easier; as Saitama put it, all he (Garou) had to do was beat up heroes. He even says that he chose it because he lacked the confidence to actually be who he truly wanted to be. Saitama then tears into Garou, saying that his plan would never work as long as he couldn't beat Saitama and Garou's "half-hearted monster hobby" would always lose against Saitama's "full-hearted hero hobby." As such, Garou's moral sloth is his own failing for his goal; he was too afraid to actually try and be The Paragon he thinks heroes should be, despite having the strength and nobility to do so.
- Flash Step: Most notably when giving his "Reason You Suck" Speech to the contingent of S-Class heroes, he frequently starts a sentence in front of one hero, and finishes it in front of another, with the heroes still looking at his old location, the implication being that he flash-stepped so fast that nobody could follow him. He also manages to close the distance between himself and many of the heroes, hit them, and then move back fast enough that it appears that the hero was hit by thin air. Happens to Sweet Mask, Child Emperor and Zombieman. He also flash-steps multiple times during his other fights.
- Foil: To Saitama. Both of them have a strong sense of morality and justice, albeit manifested in different ways. While Saitama wanted to be like a hero from his childhood who fought villains, Garou wants to be a monster who defeats heroes. While Garou is a genius fighter and a prodigious martial artist, Saitama is an untrained brawler with basic (albeit solid) fighting skills. Garou has an important moral mission he is determined to accomplish, while Saitama is just a hero for fun. Furthermore, Garou can enjoy the feeling of losing in order to improve himself to become stronger in most of his fights, while Saitama desires to have a worthy opponent to find the rush of excitement he once had while he was training.
- Also to Sweet Mask. Both desire world peace and justice, spouting melodramatic rhetoric about good and evil to make up for the fact that neither of them feel confident enough to do it themselves: Garou's plan is to force the rest of the world to become better, while Sweet Mask wants to police other heroes and create a supreme hero. While Sweet Mask is a superstar idol, Garou is a neglected underdog; while Sweet Mask is a monster playing the hero, Garou is a normal guy playing the monster. The list goes on.
- Freudian Excuse: A lot of his hatred for heroes and trying to find someone he considered to be a true hero is because he was bullied as kid by the local popular kid, and realized that all it takes to become a hero is say you're one and then have the public worship you, regardless of your actions.
- From Nobody to Nightmare: Began as a somewhat eccentric kid who thought Evil Is Cool. Became one of the strongest villains in the world, and proud of it. Except maybe not so proud about it.
- The Gift: Garou is noted to be gifted without parallel, and is capable of learning martial arts by observing them once. In addition, he experiences explosive growths in power and can adapt to any situation quickly, especially in mid combat. It is this reason Psykos chooses him to succeed Orochi as her right-hand, noting he possesses talent beyond even the Monster King's.
- Good All Along: Saitama certainly thinks so. Judging by Garou's expression when Saitama explains it, he's right. He (and the other Monsters) also note that Garou went out of his way to avoid actually killing any humans during his so-called Hero Hunt. He also reveals that Garou's threat to kill the child he spent his entire story arc protecting was a bluff by pointing that Garou was walking in the wrong direction. Saitama quickly grows bored of their fight for this very reason: Saitama became a Hero because he wanted to fight villains. Garou isn't a true villain — he's just a guy making a ruckus in Saitama's neighborhood.
- Good Thing You Can Heal: Another of his abilities: the ability to adapt his body and slowly heal himself. His body is physically battered by the end of his arc, but the man has sustained such a massive beating that it's a wonder he's even standing.
- After a few more evolutions later on, he could even regrow limbs in seconds.
- The Greatest Style: In his Awakened state, The Monster Calamity God Slayer Fist is this, which is the amalgamation of 12 separate martial arts styles he learned. Combining it with Awakened Garou's latent physical abilities lets him stand up to Saitama for a time being. Once he devolves back to a human, he seemingly loses the ability to use it.
- Guttural Growler: Garou has a very raspy voice.
- Healing Factor: At first it just allowed him to rapidly recover from injuries, though he could still be winded or exhausted afterward. As his powers evolve, it just gets even more ridiculous. By the time he's on the verge of breaking his limiter and "Awakening", he's able to heal over his rib cage effectively-being shattered by Superalloy Blackluster within minutes, while still able to keep fighting and moving like it's not bothering him.
- Hero Killer: Oh come on, it's in his villain nickname. Near the end of his arc, he beats nearly every single hero that was S-Class, including a partially weakened Tornado, and even the A-Class number 1 (which is S-Class strength-wise) without any effort. Though Saitama notes that Garou didn't actually kill any of them.
- Horned Hairdo: His hair is styled in Mishima-style horns. And as he gets stronger and stronger it gets wilder and pointier.
- How Much More Can He Take?: Hero and Monster alike are often in awe at Garou's durability and endurance, which has allowed him to push forward and keep fighting even as his muscles tear and his bones break. Even his Healing Factor only helps so much, as he's often continuing the fight even as it's in the process of working its magic. Superalloy Blackluster is left in shock when Garou is still able to keep going and launching complicated martial arts moves despite taking a blow that basically shattered his rib cage, which puts the first spark of doubt and fear in his mind that he might actually lose despite his own Nigh-Invulnerable body.
- If You're So Evil, Eat This Kitten: Saitama pulls this on Garou.
- I'm a Humanitarian: Chows down on the meat of some monsters he slaughters at one point, stating that "food's food" and he needs to restore energy. Note that many monsters were originally human.
- Hyperactive Metabolism: In chapter 134 he recovers from a beating by going to a diner and ordering all of their meat dishes (for protein and calories) and salads (for the vitamins) and washes it down with plenty of water. Right after he finishes his meal, his injuries immediately start to vanish as his Healing Factor kicks in.
- Invincible Villain: A concept that gets played with, Garou actually loses about as many fights as he wins, but with every loss he gets stronger and adapts to his opponents' fighting styles. Garou eventually does reach a point where he surpasses all the S-Ranked heroes, but he is still ultimately defeated by Saitama.
- The big takeaway from all of Garou's fights is that as strong as he is, he's only so successful because of his ability to strategize and exploit an opponent's weakness. This comes into play during the final fight with Saitama. He just kept evolving into stronger and strong monster forms, but his mind was basically deterioating in exchange for brute force. That's what sealed his defeat.
- Irony: Yells at Saitama not to underestimate him. Proceeds to underestimate Saitama. He gets reduced to a Butt-Monkey.
- Knight of Cerebus: Ultimately, this is the sort of Monster Garou wants to become — the type of monster that, once it appears, changes the atmosphere of a battle completely. He becomes capable of defeating almost all the S-Rank heroes and he actually makes Saitama fight seriously-ish, but in the end, he never manages to get Saitama to consider him a monster.
- Large Ham: He's loud and bombastic, like the cartoonishly hammy supervillains he worships.
- Lightning Bruiser: Second only to Saitama in terms of strength, speed, and durability. Word of God implies he's approximately as powerful as Boros.
- Mad Eye: As he takes more and more damage and evolves further, his right eye begins to change a darker color.
- Meaningful Name: Of the ironic type. The dreaded Hero Killer is named after a wolf, the lowest threat level classification for a monster, which only signifies a potential threat to a group of people. Turns out more accurate than not by the end of Saitama's fight with him though.
- Meaningless Villain Victory: Played with. In the case of the Hero Association officer Muffintop, Garou likened the sense of clobbering him to stepping in crap knowing full well said pencil-pushing reprobate was lying douche bag looking to cop a feel off of those girls.
- Ultimately played straight. Despite everything he does and all he's sacrificed, he still can't do a damn thing against Saitama.
- Mook Horror Show: Probably the best example, since he managed to last an entire fight against Saitama. Not only is he a category above the entire S-Class heroes, but his abilities went to the point that he could block literal light-speed punches, and cuts that could split atoms, by evolving god-like abilities in martial arts. Then Saitama, an amateur with "normal punches", crushed him over and over again, to the point that he crossed all the possible ways to defeat him. Due to this, Garou labels him as the representation of the unfairness of justice. Even becoming the "unfairness" of evil left him only as a punching bag for a couple of minutes. Though Saitama pretty much reveals the reason why is because Garou's conviction was half-hearted and couldn't beat Saitama's full-hearted conviction.
- Morality Pet: He takes a shine to Tareo and goes out of his way to protect him multiple times, since he empathizes a lot as a fellow victim of bullies.
- Mr. Fanservice: Garou has many shirtless scenes, showing off his muscular torso, shoulders, and chiseled abs. Word of God claims that Garou's back is a reference to Bruce Lee's muscular back.
- No-Sell: He manages to evade or deflect all of Saitama's normal attacks at the beginning of their battle and announces to the latter that he will ultimately lose because Garou's combat style will eventually prevail over Saitama's combat style. Too bad for Garou that Saitama decided to show him a little bit of his serious side.
- Nightmare Fetishist: Ever since he was a kid, he would always play the role of the monster that the heroes fight. Always. Of course, he respected the monsters due to their more often than not superior effort. Unfortunately, certain kids took advantage of this to have an excuse to beat him up. This just made him more determined to become the sort of monster that can beat self-centered, self-proclaimed "heroes" like them. Ironically, if it was the other way around, he would've been a lot like Genos. And it later turns out he never really went evil, either.
- Noble Demon: He definitely shows a degree of martial honor and is upset by crueler tactics or sleazy individuals, though he claims otherwise. Saitama realizes, if anything, the Demon part is the one that's suspect. A certain manipulative Skirt Chasing HA administrator who milks the company budget to pick up chicks found this out the hard way.
- Nonchalant Dodge: It's repeatedly noted in his manga incarnation that he dodges attacks and projectiles with a minimum amount of movement. Yet, the trope is subverted because Garou does take the dodging seriously as his human body is still vulnerable to blows and projectiles. It's just that for a martial artist of his level, it's the most efficient way of evading damage.
- Oh, Crap!: Breaks instantly out in cold sweat in the manga when he first meets Saitama who no sells Garou's sneak attack with the highly sophisticated method of not reacting to it at all. Garou forgot about this encounter afterward.
- Has a series of this during his fateful confrontation with Saitama. Whenever Garou thinks he has cornered Saitama, he is proven wrong. Becomes the cause of his Villainous Breakdown.
- Older Hero vs. Younger Villain: He is the "younger villain" being 18-years-old, while Saitama is the "older hero" being 25-years-old.
- One-Man Army: As Awakened Garou, he's so strong that he can simultaneously defeat most of the S-Class heroes while barely trying.
- One-Winged Angel: Played straight when he becomes a bald, horned figure to mirror Saitama's own generally basic appearance, becoming what Black Sperm calls Awakened Garou. Then inverted when he starts trying to milk it further.
- Parody Sue: Garou is a parody of Villain Sue, being an unstoppable force that keeps getting more powerful with no real explanation and trounces everyone until Saitama comes along. However, his status as the most powerful antagonist faced yet is effectively neutered due to how he's never killed anyone besides monsters and was never planning on it. Garou was never an actual threat and halfassed trying to be a villain.
- Pet the Dog: When Metal Bat's little sister throws herself in between the two of them, Garou actually follows her request to stand down, claiming he's too busy to keep wasting time on Metal Bat. And when a Monster Association goon considers grabbing Zenko as a hostage, Garou kills him, supposedly because he didn't like being watched.
- Poke the Poodle: He doesn't pay for his meals. And ultimately, his entire "villainous" career-compared to monsters in general, the property damage he does (accidentally) and repeated nonlethal humiliation of heroes is barely worth mentioning.
- Power Makes Your Hair Grow: His hair grows outwards wildly, and becomes more horn-ish as he fights and becomes stronger until he transforms into a mysterious being and his hair becomes real horns. He goes bald in exchange, though.
- Pummel Duel: Manages to endure Saitama's two-handed Consecutive Punch Combo for a while. The is quite an achievement, considering what normally happens when Saitama uses the one-handed version.
- Rapid-Fire Fisticuffs: As a practitioner of Bang's Water Stream Rock Smashing Fist, he's capable of this.
- Razor-Sharp Hand: He starts using the Whirlwind Iron Cutting Fist after beating Bomb, albeit on a lower level. He could karate-chop a cup perfectly in half before then, though.
- "Reason You Suck" Speech: After Garou goes on a rant when Saitama defeats him and learns that his heroism is just a hobby, Saitama picks up on Garou's true nature. He proceeds to spell it out in front of Garou along with why Garou was never gonna defeat him:Saitama: So you did have an "image of an ideal hero" inside of you. I see now. I now understand what you wanted to do. Even though you said you wanted to be a "monster of absolute evil"... What you really wanted to be was a hero. But you compromised and decided to be a monster. To bring about world peace, you took the easy route, thinking a monster's job was quicker and easier than a hero's. A monster's role is simpler after all, all you had to do was defeat heroes. It's perfect for someone with no confidence like you. BUT YOU CAN NEVER DEFEAT ME. And peace made by ruling the world with fear can't succeed as long as you can't defeat me. So it will never work. It's absolutely impossible for you. Because if it's your compromised monster hobby vs my serious hero hobby, even if that's all I had, I still wouldn't lose! It was a mistake to lower the hurdle right before the goal. A half assed objective just can't succeed.
- Retired Badass: After the Monster Association saga, Garou takes Saitama's words to heart and tries to live a peaceful life while atoning for his misdeeds against society. He starts looking for simple employment, becoming... the Job Hunter.
- Reused Character Design: Give him a few guns and make him wear football gear, he'll look like Yoichi Hiruma from Murata's previous work Eyeshield21.
- Rooting for the Empire: In-Universe. As a child he was more interested in villains than heroes. This ended up adding more to his current-day behavior as other children turned against him when he talked about it.
- Scarf of Asskicking: As he progressively gets stronger, he eventually gets an ominous scarf.
- Shadow Archetype: To Saitama, but not for the reasons you might think. While Saitama grew up wanting to be a hero and Garou grew up wanting to be a villain. Garou made a mistake. Garou always liked villain designs in his cartoon show as a kid, but he didn't empathize with the villains because they were evil. He adored their personalities and designs over the show's Invincible Hero. He convinced himself that he would rather be a monster and that he hated heroes, but what he hated was heroes that weren't ideal or who were just plain bland. When it came to Tarou, he just couldn't stand seeing the kid get hurt like he was as a kid and defended him with his life. With the heroes, he just wanted to upstage them and knock them down a peg, not kill them. He didn't have the same qualms about killing monsters especially when they tried to hurt innocent people, especially kids. In the end, while he gained power in the same way Orochi and Saitama did, he couldn't break the final limiter because he wasn't enlightened like Saitama is. The reason why as Saitama implies is because Garou's conviction was half-hearted, being too unconfident to try and be the hero he really wanted to be.
- Slasher Smile: Wears this expression a lot whenever in a fight.
- Spell My Name with an "S": The Viz translation shaves the "u" off the end of his name, leaving it as "Garo" so that English readers know to pronounce it [garo] instead of [garu].
- Strong and Skilled: Garou specializes in Bang's martial arts techniques and has a lot of raw power to back it up, but can subvert this trope as he prefers using his skill even though he has a lot of strength to back up his fighting ability. Especially when he amps up his abilities in his One-Winged Angel form to where he can fight Saitama at "Semi-Seriously".
- Super Strength: He is strong enough to smash through concrete walls and crumble them to bits.
- Super Speed: Fast enough to outspeed Lightspeed Flash as Awakened Garou.
- Super Toughness: Durable enough to survive several punches coming from Saitama and able to walk away from it relatively unharmed as Awakened Garou.
- Taking a Level in Badass: During the entire Monster Association Arc we see Garou taking several levels. From a guy that had difficulty in defeating a lower S-Class hero, to one that can defeat much stronger S-Classes. At the last part of the arc, he curbstomps several S-Class heroes and gives Saitama a slightly tough fight.
- Talking the Monster to Death: It's very gradual, but Garou's worldview is very slowly deconstructed. Saitama breaks it by asking simple questions during the fight (it didn't hurt that Garou's previous responses stopped working), and even after he's beaten ("Are you okay with that?") Garou seemingly decides to stop being a villain after seeing the kid that constantly got kidnapped throughout the arc stick up for him, simply because Garou saved his life every time, and retreats.
- Teens Are Monsters: He is an 18-year-old teenager who sometimes refers to himself as the "human monster".
- A Twinkle in the Sky: Eventually Saitama uppercuts him so hard he flies into orbit... AND THAT STILL DOESN'T KILL HIM. This just makes him disappointed that Saitama's strength is unfair, so he just resolves to become a "unfair Evil" in order to stand against him and he returns in a bigger form.
- Underdogs Never Lose: He invokes this a lot at the beginning of the story, coming out victorious in situations where he's outnumbered and outskilled multiple times. It's almost ludicrous. However, as time goes on and he encounters stronger enemies such as Overgrown Rover and Orochi, he begins to lose fights more and more.
- Villainous Breakdown: He starts losing it the longer he fights with Saitama and seeing how outclassed he is.
- Walking Spoiler: His true motivations and the truth about his actions are major spoilers.
- Weak, but Skilled: Subverted as for extremely relative values of "weak" he is far from it, but Garou is noted as posing a particular threat because, while previous monsters relied on brute strength to overwhelm heroes, Garou fights with actual martial arts and specializes in redirecting his opponents' attacks instead of just countering them. Basically, his fighting style is geared specifically towards defeating heroes. Once he goes One-Winged Angel, he becomes this especially in comparison to Saitama, as while he's still much weaker (something he himself admits), he completely surpasses him in terms of martial arts and even manages to force him to fight "Semi-Seriously".
- Well-Intentioned Extremist: For all of his posturing, this is what he really is-by forcing the world to unite against his "evil", he's unifying it. That, and he really isn't a cruel person at all. Deconstructed by Saitama who notes his plan could only work by defeating Saitama and Saitama would not lost against Garou because Garou lacked the conviction to be The Paragon he really wanted to be.
- What Measure Is a Non-Human?: Played with — Garou has a interesting mindset on what a monster should and shouldn't do, and other monsters question if he's either too human or an outright scary, wild force of nature.
- Wild Card: Garou doesn't have any qualms about massacring weak "villains" or monsters that disappoint him. He also has a weird habit of letting the Heroes he savagely beats up live, simply so they can get stronger for the eventual rematch.
- The Worf Barrage: In the end, his self-evolution-adaptability powers. Each hit of Saitama literally made him stronger and stronger until he became a demonic god-like being... and then it simply couldn't go higher, and ended up regressing him with each subsequent punch ultimately reverting him to his human form. Saitama literally killed his ultimate villain concept of Came Back Strong, one attack at the time. It's implied that it's because deep down, he actually doesn't want to be a monster.
- World's Strongest Man: At the apex of his power, Awakened Garou, he's strong enough to wipe the floor with the entire S-Class of the Hero Association save BLAST. He's at least as strong as Lord Boros because he was capable of lasting a signifigant amount of time in a one on one scrap with Saitama. It's ultimately unclear how strong he is really because he purposely fights in a way that ensures the people he attacks don't die and only obtain serious injury.
- Would Hurt a Child: Garou has no hang-ups about punching Child Emperor hard enough to send him flying through the air. He also taunts the defeated S-Class heroes by threatening to kill the boy who has been used as a hostage throughout the story arc. This was subverted, however, as Saitama calls this bluff, pointing out that Garou was walking away from the boy instead of towards him (Saitama was the only person whose night vision was good enough to see this).
- You Are What You Hate: After finishing his desperate Motive Rant, he becomes outraged that Saitama isn't acting as a proper hero... which means that for all his hatred of heroes, he did have a concept of an ideal hero after all, and his actions, at their core, were born from a desire to make the world a better place, as described below.
- Younger Than They Look: Garou looks like he is in his mid-20s, however Chapter 134 reveals that he is only 18-years-old.
- Zero-Approval Gambit: Revealed to be his true modus operandi: he believes that only a grand, unifying evil can force the world to set aside their own differences and stop oppressing the weak. Saitama calls him out on this as since not even Garou seems to really approve for it; his gambit was the result of compromise and thus lacks full conviction.
Voiced by: Yasutoshi Tokumoto (Japanese), Tom Fahn (English), Alan Prieto (Latin American Spanish)
Debut: Chapter 2 (Webcomic and Manga), Episode 1 (Anime)
Disaster Level: Tiger
A man who became a monster from eating too much crab, and who wouldn't hesitate to kill kids making fun of him. He was the first kill of Saitama's hobbyistic heroism.
- Alien Blood: His blood seems to be yellow along with the rest of his organs as shown when Saitama rips his eye out. Ironically though, crab blood is translucent blue in real life.
- Attack Its Weak Point: The carapace may be tough, but those eyes on stalks are convenient weak spots.
- Disproportionate Retribution: The big-chinned child drew nipples on his shell with a magic marker. His reaction is trying to hunt down and kill the kid. The same thing happens to anyone who even off-handedly comments on his appearance.
- Evil Is Petty: Primarily attacks people who make fun of his appearance or otherwise inconvenience him, no matter how slightly.
- Eye Scream: Saitama tears off his eyestalk... and the entirety of his insides with it.
- Giant Enemy Crab: A gigantic humanoid crustacean and Saitama's first real foe.
- Ludicrous Gibs: After Saitama tears off his eye, all the crab meat inside starts rocketing out like a firehose, covering the area.
- Pet the Dog: He was willing to spare Saitama since his "lifeless eyes" reminded Crablante of his own.
- Signature Laugh: "Buuu-ku-ku-ku-ku!" The dub gives him a Mr. Krabs-like laugh.
- Starter Villain: The very first monster Saitama fights, in-universe, before his trainingnote — and the one who causes him to start training in the first place. Also relatively quite easy to kill.
- Superhero Origin: Parodied, Crablante turned into what he is simply by eating too much crab meat.
- Super Strength: He is powerful enough to shatter the earth with his claws, and easily beats around Saitama as he was nowhere near as strong as he is now.
- Tattoo Sharpie: Crablante had nipples drawn on him by a kid using a permanent marker. Crablante notes that the marker could be scrubbed off, but as he has two giant crab pincers for arms, he can't possibly clean it off himself.
- Would Hurt a Child: He attempts to murder a little boy for the crime of drawing nipples on Crablante's chest with a sharpie pen.
Voiced by: Ryusei Nakao (Japanese), Christopher Sabat (English), Marcos Patiño (Latin American Spanish)
Debut: Chapter 1 (Webcomic and Manga), Episode 1 (Anime)
Disaster Level: Dragon
A being which sought to stop pollution and wipe out humanity for the sake of Mother Nature. He is the first enemy we see Saitama effortlessly obliterate, establishing just how overpowered Saitama really is.
- Alien Blood: His blood is dark green.
- Barbie Doll Anatomy: Completely naked but possesses no attributes.
- Captain Ersatz:
- Gaia's Vengeance: He considers himself to be an incarnation of nature's wrath, sent to wipe out humanity, which he thinks is an infection, as well as a vaccine to protect Earth against future infections. This is parodied overall; many old-school Japanese hero shows have similar villains, almost all of which are designed to teach the viewers and/or the characters a Green Aesop. However, Vaccine Man is immediately OHKO-ed by Saitama upon his introduction, and nobody learns anything from him.
- Having a Blast: One of his powers is to create energy balls that can explode entire city blocks.
- Kill All Humans: His solution to save the planet.
- Killed Mid-Sentence: Twenty words isn't nearly enough to tell a non-half-assed backstory adequately before Saitama gets bored.
- Large Ham: Before he's killed by Saitama, he makes a big entrance and declares his Evil Plan in a grand and showy manner.
- Ludicrous Gibs: His final fate is having his guts splattered all over the city he just destroyed.
- One-Winged Angel: He starts bulking up to a monstrous degree in order to fight Saitama. Not that it helps.
- Person of Mass Destruction: Destroys a city in his first (and only) appearance.
- Sizeshifter: Is able to increase the size of his body.
- Starter Villain: He's the first monster shown to be fought by Saitama and simply exists to show how overpowered he is. Unusually for the trope, he is one of the more powerful villains of the series.
- We Hardly Knew Ye: Dies within a few panels of being introduced in order to show the premise of the series.
- Would Hurt a Child: It's a given since he really wants to Kill All Humans, so he'll spare nobody. After destroying most of a city and killing countless people as a result, he walks up to a little girl who survived and tried to crush her with his bare hand (fortunately Saitama came to her rescue).
- You Have GOT to Be Kidding Me!: Doubles as Lampshade Hanging.Vaccine Man: You're a fast one. Who are you?
Saitama: Just a guy who's a hero for fun.
Vaccine Man: FOR FUN?! You're kidding. What kind of half-assed backstory is that?! Mine is far superior!
Oldface & Beefcake
Voiced by: Takuma Suzuki (Oldface) and Shinya Hamzoe (Beefcake) (Japanese), Kirk Thornton (Oldface) and Bryce Papenbrook (Beefcake)(English), Miguel Angel Leal (Oldface) and Adrián Fogarty (Beefcake) (Latin American Spanish)
Debut: Chapter 1 (Webcomic and Manga), Episode 1 (Anime)
Disaster Level: Dragon
A pair of brothers. Oldface is a mad scientist who developed a super steroid called Biceps Brachii King, while Beefcake is a body builder whom the formula mutated into a colossal giant.
- Adaptational Badass: Although Beefcake is always an absolute giant, he is much larger in the anime, where his footprints are kilometers long and span several city blocks in both length and width.
- Astonishingly Appropriate Appearance: Coupled with Meaningful Name: Oldface has a prematurely wrinkled face, and Beefcake is a musclehead.
- Attack of the 50-Foot Whatever: Beefcake gains a truly terrifying size. Skyscrapers only go up to his ankle.
- Barbie Doll Anatomy: Averted. Saitama demands Beefcake put on some pants, though nothing is shown to the audience thanks to literal clouds being used as Censor Steam.
- Big Guy, Little Guy: Before and especially after Beefcake's transformation.
- Big Little Brother: Beefcake was already the bigger of the two pre-transformation. Needless to say he is afterwards.
- Black Comedy: Oldface tells his brother to kill the guy on his shoulder. Beefcake does as he is told... but goes for the wrong shoulder, the one his brother is on, causing his brother to get reduced to bloody mush to the despair of Beefcake.
- Brains and Brawn: Literally the name of their team.
- Captain Ersatz: Beefcake is one to the Colossal Titan. The English dub even has him voiced by Eren Jaeger's voice actor.
- Drunk with Power: Both Oldface and Beefcake relish in the destruction they are now capable of. Oldface cackles psychotically at the thought of thousands dying at Beefcake's hand, while Beefcake is overjoyed at finally achieving his dream of being the strongest in the world, or so he thought.
- Dub Name Change: Sometimes Beefcake is translated as simply "Marugori" and Oldface is "Fukegao".
- Dumb Muscle: Beefcake accidentally kills his own brother just because he tried to smash Saitama... who was on his other shoulder.
- Exact Words: Oldface, while on Beefcake's right shoulder, commands Beefcake to kill Saitama who is on his left shoulder. However Oldface ordered him to "kill the man on your shoulder!" So Beefcake kills him by accidentally slapping the wrong shoulder.
- Little Big Brother: Beefcake was the larger of the two before he even drank the serum. And after his transformation... well it goes without saying.
- Mad Scientist: Oldface makes a Super Serum that turned his brother into a stupid and super strong giant, so they cause destruction.
- Magic Pants: Averted. Beefcake's transformation destroyed all his clothes, pants included, Instead Censor Steam is used to cover his private parts.
- Not So Different: Saitama understood exactly how Beefcake felt, being the strongest in the world feels utterly meaningless.
- Person of Mass Destruction: Beefcake. He can sweep multiple city blocks clean with a literal wave of his hand.
- Roaring Rampage of Revenge: Beefcake goes on one after accidentally killing Oldface and blaming it on Saitama.
- Sibling Team: The Brain and Brawn brothers.
- Super Serum: Oldface makes one that turns Beefcake into an immensely giant man.
- Sympathy for the Devil: When Beefcake accidentally kills his brother and sees his strength as a curse, Saitama says he knows how he felt... before killing Beefcake with one punch.
- Unskilled, but Strong: Beefcake relies solely on his brute strength and has no technique to his fighting, much like Saitama.
Voiced by: Ariumi Naito (Japanese), Tara Sands (English), Marisol Romero (Latin American Spanish)
Debut: Chapter 20 (Manga), Episode 6 (Anime)
Disaster Level: Tiger
A seaweed-haired monster roaming about Z-City.
- Ambiguous Gender: On The Other Wiki, they aren't referred as a he or a she and have a very androgynous appearance and voice, assuming gender can be applied to them at all.
- Affably Evil: Is rather chirpy and bordering on Friendly Enemy-levels of attitude, even in combat. They even regard Spring Moustache as a Worthy Opponent.
- Alas, Poor Villain: In the manga at least, we get a shot of them weeping woefully on the ground after Saitama ripped off all of their kombu and used it for soup stock. Though considering what Saitama does to most monsters that incur his wrath, they got off pretty easy.
- Killer Rabbit: You wouldn't expect a seaweed-hair monster to be a threat capable of hospitalizing two high-ranking A-Class heroes without difficulty, but it is and it does.
- Irony: He came to Saitama's neighborhood looking for a legendary monster rumored to live there. No guesses needed to figure out who the "monster" is.
- Not Quite Dead: The manga reveals that Saitama tore off their kombu without actually killing them.
- Offscreen Moment of Awesome: We don't get to see how Saitama deals with it. But it involved breaking a building in two.
- Prehensile Hair: Well, technically it's not hair but it sure fills this role.
- Worthy Opponent: Considering that they are in awe after Spring Moustache defends against their attacks with little difficulty, it's easy to tell they view him as this.
Deep Sea King
Voiced by: Rikiya Koyama (Japanese), Keith Silverstein (English), Carlos del Campo (Latin American Spanish)
Debut: Chapter 24 (Webcomic), Chapter 23 (Manga), Episode 7 (Anime)
Disaster Level: Demon
The leader of the Seafolk, and the first monster to have his own arc. He sought to slaughter the humans and control the surface world. His impressive abilities match even S-Class heroes.
- Acid Attack: He can spit out globs of powerfully corrosive acid.
- Alien Blood: He bleeds blue.
- Authority Equals Asskicking: He's the leader of the Sea Folk, and is by far their strongest member.
- Ax-Crazy: He delights in murder. So much so that he broke into a shelter full of civillains hiding from him, just so he could kill them all.
- Battle in the Rain: For once, it serves a purpose other than just being dramatic: the rain actually increases the Sea King's power significantly.
- Cool Crown: Goes with being King.
- Combat Pragmatist: Outmatched? Target an Innocent Bystander, a little girl no less, instead of the hero and force them to take the acid glob.
- Elemental Absorption: Water. While he can survive out of water for extended periods of time, he shrivels into a smaller, albeit still formidable, form. Being exposed to water allows him to hulk out into his true form, which is enormous and far more powerful.
- Hate Sink: He is an egomaniac who sees himself as superior to everyone else and lives to murder people weaker than himself.
- Healing Factor: While shown to be highly resistant to attacks, the Sea King is capable of recovering from his injuries at an extreme rate, as seen when an injury he received from Genos, an S-Class hero, healed while they were still fighting.
- I Am Not Left-Handed: After curb-stomping Pri-Pri Prisoner in a fight, he reveals that he had been fighting in a weakened dehydrated form the entire time.
- Knight of Cerebus: Deep Sea King's episode is consistently darker than anything before or since in an otherwise lighthearted series, personally managing to defeat every single hero that has enough confidence to face him, in which 2 of them are low-ranked S-Class heroes. He instills a greater sense of dread within the narrative by showing just how dangerous attacks by monsters are for people who aren't Saitama. That is until Saitama finally decides to face him...
- Lightning Bruiser: Strong enough to curb-stomp Puri-Puri-Prisoner and fast enough to keep with Sonic's speed.
- Macho Camp: ...Maybe. Has a style of speech that is unmistakably stereotypical camp. It's also why his 'dehydrated' form has hearts for nipples. Also a weird example of Adaptational Sexuality, as because it's only hinted at through his style of speech and not any kind of content or actions, this aspect of him is difficult to translate (eg: fan translations). Thus, while their fight is obviously an Expy Mirror Match in Japanese, and gives slightly more weight to Puri-Puri-Prisoner's having taken his advice, this aspect is completely lost on foreign audiences.note
- No Celebrities Were Harmed: Keith Silverstein does a pretty good Tim Curry impression for the English version.
- One-Winged Angel: His more humanoid form is the result of him spending an extended period of time out of the water and dehydrating. The rain (and the water in general) allows him to return to his much stronger original form.
- Overly Long Tongue: ...with mouth. He describes it as a moray eel, and given that he can still talk after Sonic slams his mouth shut and cuts most of it off, it might not be his actual tongue.
- Rapid-Fire Fisticuffs: He seems to have a preference for combo attacks, attacking his opponents mostly with a barrage of punches.
- Requisite Royal Regalia: Wears a regal crown and an ermine cape, but strangely very little else.
- Slasher Smile: Not helped by his very sharp teeth.
- Small Name, Big Ego: While he's not a small name and is actually quite powerful, he thinks that he's the World's Strongest Man by virtue of being the king of the seas since all life originated from the sea, never mind that there are many more heroes and monsters out there that outclass him. Saitama quickly proves him wrong.
- Sorting Algorithm of Evil: Subverted. Despite being introduced later in the series and lasting longer, he's actually much weaker than previous monsters like Vaccine Man, Beefcake, and Carnage Kabuto. He only gets more screen time because he faced off against weaker heroes while Saitama was busy getting lost.
- Super Spit: He can shoot out acidic saliva from his mouth that is extremely corrosive, as it melted Genos' metallic body almost completely.
- Super Speed: He boasts an exceptional amount of raw speed, seen when he was able to sneak up on Lightning Max (whom had been observing him from a distance) instantaneously, catching the A-Class hero well off guard. Under the rain, he can even keep up with Sonic's speed.
- Super Strength: Comparable to an S-Class hero from the get-go, and it increases even further when in contact with water.
- This Cannot Be!: After getting a hole punched through him by Saitama, his final expression screams this before he keels over.
- Averted in the anime; one of his eyes is dangling out of its socket, and his face resembles a dead fish, implying he was killed instantly.
- To Serve Man: He wants to turn humanity into food supplies for the Sea Folk.
- Underwear of Power: His attire oddly consists of only a crown, a cape, and underwear.
- Wake-Up Call Boss: In the anime, he's the first villain to last more than one episode. He also defeats several other heroes including two S-Class ones, albeit the lowest-ranked ones.
- Weak to Fire: Downplayed, but Genos' flame-based weaponry seems particularly effective against him, even forcing him to resort to dirty tactics because he was losing the fight. While it's never said that he is weak to fire and you could make the argument that Genos' power simply overwhelms him, the Sea King relies on hydration to reach his strongest form, excessive heat may dehydrate him, thus sapping his strength.
- Would Hurt a Child: Oh yes he would. During the Deep Sea King's fight with Genos, he even went out of his way to spit acid at a little girl just for cheering on Genos; and she would've melted had the cyborg hero not jumped in front of the corrosive fluid to save her.
Voiced by: Christopher Corey Smith (English)
Debut: Chapter 33 (Webcomic), Chapter 30 (Manga), Episode 10 (Anime)
Disaster Level: Unknown
The ruler of the skies, seeking to take over the world with his minions, the Skyfolk. Unfortunately, his conquest was cut short by the Dark Matter Thieves.
- Bird People: His race are winged humanoids with bird-like traits.
- Breath Weapon: He and his Skyfolk can fire energy blasts from their mouths.
- Tengu: The Sky King and his minions resemble Tengu.
- Underestimating Badassery: He believed that he could take down the Hero Association's main headquarters. However, he did not even get the chance to be proven wrong...
- We Hardly Knew Ye: He and the Skyfolk are unceremoniously slashed into bits by Melzargard just as their invasion begins.
The Mad Cyborg
Disaster Level: Unknown
An unknown Cyborg that had destroyed Genos' hometown, causing the latter to become a cyborg himself in order to avenge his deceased family.
- Ax-Crazy: It's even in its' title, and its backstory involves rampaging Genos' hometown and slaughtered everyone besides the latter.
- One-Man Army: This thing can easily destroy an entire village on the outskirts by itself, meaning that it's very powerful and dangerous. Also, it's confirmed by Drive Knight and Dr. Kuseno that the Mad Cyborg had rampaged against numerous other villages before Genos' hometown.
- Only Known By His Nickname: It's only called the "Mad Cyborg", "Crazy Cyborg", or the "Rampaging Cyborg".
Disaster Level: Unknown (possibly God)
A mysterious and powerful being. It gave Homeless Emperor his powers and played a major role in the creation of Psykorochi.
- Absolute Xenophobe: It hates humans with a passion and wants them all dead, which is why it gave Homeless Emperor his powers and gave newfound abilities to Psykorochi.
- Adaptation Expansion: He plays a larger role in the manga. Specifically fusing Psykos and Orochi together and being the main reason Blast is so busy.
- Arch-Enemy: He appears to be this to Blast.
- Eldritch Abomination: It appears to Psykos as a massive planetoid comprised of what appears to be brain cells.
- Expy: Of the Anti-Spiral of Tengen Toppa Gurren Lagann. Both hate humans with a passion for some reason, they both live in Another Dimension and they even have a somewhat similar design and are both shown to be super powerful in comparison to everyone else except the main character.
- Greater-Scope Villain: It is possibly a God-level threat and probably the one behind all the events related to the Monsters, as it's implied to be the "God" of all Mysterious Beings.
- Humanoid Abomination: It appears to Homeless Emperor as a giant humanoid with Creepily Long Arms, covered in scar tissue from head to toe and with no face.
- The Man Behind the Man: Psykorochi obtained their new powers from this creature as a representative of its will.
- Only Known by Their Nickname: It is called "God" by Homeless Emperor, but we don't know how it calls itself.
- Super Empowering: Gave Homeless Emperor his powers, and took them from him as well. It gave Psykorochi a dramatic increase in terms of abilities, and it may also be the source of Garou's powers.
- Walking Spoiler: This thing spells major villain in the future, is super important to the plot and so far only appeared in a few panels in both the webcomic and manga.
- You Have Failed Me: The reason it kills Homeless Emperor.
A group of underground monsters bent on taking over the surface world. They are at odds with the Seafolk and Skyfolk as well, but the relationship between these groups is not explored as none survive the series long enough.
- Back from the Dead: Resurrected by Phoenix Man in his battle with Child Emperor.
- Brick Joke: A couple of the resurrected creatures appears to be as big as the ones that Saitama dreamed about. Perhaps he just wiped them out too quickly.
- Dreaming of Things to Come: Not them, but Saitama has a dream about them taking over the surface world the night before they reveal themselves.
- Killed Offscreen: Apparently didn't submit to or were declared too weak to join the Monster Organization. (While Genus could have done it, he would have needed to know about the Monsters Organization's lair, which he doesn't, given where their corpses were found). Oddly, they were dumped into a deep pit of water instead of being fed to Orochi.
- Small Name, Big Ego: At least their king was. He thought he could take over the surface world, but given how small he was and how doofy he and his minions looked compared to their dream counterparts, they were definitely not strong enough to beat the heroes.
- What Happened to the Mouse?: They lived underground and popped up in Z City where Saitama lives and where the Monster Organization eventually set themselves up. It was possible they could have moved and they don't come up later on in the Webcomic, but the manga shows their dead, rotting bodies in the flooded area of the monster's base. Phoenix Man's thoughts imply the Monster Association had them killed.
- Worthy Opponent: What Saitama declares them to be in his dream and the feeling was mutual. In reality, they are a case of Small Name, Big Ego.
House of Evolution
Voiced by: Daisuke Namikawa (Japanese), Ray Chase (English), Christian Strempler (Latin American Spanish)
Debut: Chapter 7 (Webcomic & Manga), Episode 2 (Anime)
The founder of the House of Evolution, whose dream was to hasten the evolution of humanity past its limits through artificial methods. He set his sights upon Saitama upon seeing his immense strength - much to his own detriment.
- Bait-and-Switch: His introduction almost set him up to be a Big Bad with a god complex who couldn't be reasoned with. However Saitama beating Carnage Kabuto abruptly shocked him into a HeelFace Turn and he abandoned all his thoughts of villainy.
- Also, everything about his modus operandi: an evil scientist with an army of genetically engineered monsters all sharing the same theme and countless identical clones, seem to be setting him up as a recurring villain or even the hero's main nemesis... Yet he reforms after a single encounter with Saitama.
- Break the Haughty: Saitama inadvertently does this by entering his "House of Evolution" and casually destroying Carnage Kabuto, whom he considers the proof of his belief in artificial evolution.
- Comical Overreacting: When he talks to Zombieman about Saitama, he says that the latter had paid a terrible price for his strength... he went bald. After a moment, he also adds in the part where Saitama is feeling complete disassociation from humanity and is progressively being distanced from his own, but the baldness came first.
- Cut Lex Luthor a Check: Sort of. After he's defeated, he devotes his genius to running a takoyaki stand using his genetically-engineered generating octopi. It's perhaps not the most practical thing he could do with his genius, but he seems to be happy.
- Evil Genius: It's even in the name itself.
- Evil Old Folks: He is over 70 years old, but doesn't looks it thanks to having used a youth serum.
- Evilutionary Biologist: He creates genetically-spliced monstrosities out of his extreme contempt for regular old human beings.
- Expendable Clone: Played straight as well as inverted. He even considers himself expendable.
- Four Eyes, Zero Soul: Glasses? Check. Evil? More or less, though he more doesn't exactly like people.
- HeelFace Turn: Sort of. Having been psychologically beaten, he decides he's done with evolution and decides to open a takoyaki stand.
- Karma Houdini: Despite having unleashed Mosquito Girl (who killed a lot of people), sending his minions to attack Saitama, and creating Carnage Kabuto (who is implied to have killed plenty of people), he gets off scot-free short of the injuries he sustained at the hands of Carnage Kabuto. It helps that he decided to put being a supervillain behind him.
- Know When to Fold 'Em: After being defeated, he decides to devote his life to running an otherwise entirely-normal takoyaki stand, using regenerating octopi for meat.
- Identical Twin ID Tag: Unlike his lookalike clones, he parts his hair on the opposite side.
- Lack of Empathy: He has difficulty empathizing with people, paired with his drive to improve the human form through artificial evolution, he feels that the rest of humanity are practically lowly animals.
- Mad Scientist: He abuses his great intellect to create homicidal monsters after all.
- Maker of Monsters: He's an Evilutionary Biologist with a god complex who creates all kinds of monsters, making powerful Bioweapon Beasts that can easily destroy an entire city.
- Meaningful Name: Genus looks like "genius". It is also a biological term, suggesting his mad science specialty.
- Me's a Crowd: He created countless copies of himself. They are actually his employees and he doesn't seem to care much about them.
- Mistaken for Gay: A throwaway joke used when Saitama was told that the scientist had "a great interest" in his body... Of course, he is only interested in Saitama's strength.
- Mr. Exposition: He provides the closest thing to an explanation we've gotten so far for Saitama's strength and the nature of Mysterious Beings.
- Nice Job Fixing It, Villain!: Created Zombieman who became one of the toughest superheroes around. He actually seems impressed and vaguely proud that Zombieman chose the hero life when they meet again. He is still slightly annoyed that Zombieman wrecked his experiments when he escaped though despite having given up that life.
- Older Than They Look: That's not a young man in his late twenties you're looking at — it's a man who reached his seventies, upon which he discovered the secret to regaining his youth, and revitalized himself. As for his clones, it's the other way around, having been around for only a short amount of time but the same biologically as him in his youth.
- Omnidisciplinary Scientist: His backstory implies that he was an expert in several fields, though genetics became his specialty.
- Sherlock Scan: After seeing Saitama beat his ultimate monster, he correctly deduces that the man isn't just powerful, but that his power is without limits. This is proven true in Saitama's fight with Garou. Like Garou, Saitama gained more and more power each time he was heavily injured as Lord Gyoro-Gyoro's experiments proved. However, Garou and Lord Orochi eventually hit a limit they couldn't break while Saitama scattered that upper limit perhaps due to having an Enlightenment Superpower of a sorts.
- Social Darwinist: He believes humanity should use its expertise to accelerate their evolution to become stronger and smarter. When his ideas didn't get support, he resolved to build a utopia shaped by and for himself.
- Sole Survivor: After Saitama and Genos destroyed the House of Evolution and killed all of the members... Apart from some small fries. A picture in the artbook implies that Mosquito Girl may have survived as well (showing her fixed up with artificial limbs and working at his takoyaki stand), although whether it's canonical or not is unclear.
- They Called Me Mad!: In his youth, he called for humanity to find new ways to evolve. He didn't receive any mainstream support, and decided to go about it by himself.
- World's Smartest Man: Doctor Genus is implied to be this. His intellect was so advanced that he soon became disillusioned with the rest of humanity and could find no one else able to keep up with his level of thinking. He soon came to believe humanity was too far behind him and sought to help the human race evolve so that he would no longer be alone.
- You Are Number 6: While he wears dark clothing, his clones wear white jumpsuits and are differentiated by the number on their shirts.
Voiced by: Miyuki Sawashiro (Japanese), Cristina Valenzuela (English), Adriana Nuñez (Latin American Spanish)
Debut: Chapter 5 (Webcomic & Manga), Episode 2 (Anime)
Disaster Level: Demon
A prototype mutant human-mosquito hybrid created by Dr. Genus. She faced Genos in Z-City, and her defeat at the hands of Saitama is what informed Dr. Genus of Saitama's existence.
- Adaptational Attractiveness: Mosquito Girl in ONE's style is essentially a woman's head and upper chest stuck onto a mosquito body, with her arms and legs being far more shriveled and insectile. Murata designs her more as an attractive woman with mosquito features, with a defined lower body and even hips.
- Axe-Crazy: She's definitely quite gleeful about draining people dry to boost her strength, and when she fights, she really gets into it.
- Barbie Doll Anatomy: Her crotch isn't drawn at all, and her nipples only appear as subtle small bumps on her chest.
- Bishōnen Line: She looks less insectoid after her transformation. She was still cute before, though.
- Blood Lust: Well she is a mosquito, kinda a given and it's what powers her up.
- Body Horror / Fan Disservice: While her human body is very attractive, her limbs are indeed those of an actual mosquito. They look quite creepy and offputting.
- The Beastmaster: She can control a huge swarm of mosquitoes.
- Cute Monster Girl: Given her Adaptational Attractiveness thanks to Murata style.
- Drunk with Power: Somewhat. She seems suave, but after absorbing all that blood she becomes much more unhinged, complete with Slasher Smile and shrunken eyes. Either that or she was always that crazy to begin with and just attempted to hide it.
- Flies = Evil: There are more than enough mosquitoes at her disposal to drain her victims of literally all their blood.
- Full-Frontal Assault: She is stark naked, as you can see in the manga when her belly button is clearly visible, and she doesn't seem to wear anything other than having body-paint or body coloration.
- Glass Cannon: Very, very fast and powerful, shredding Genos easily — but he didn't seem to have much trouble with ripping her lower legs clean off. So naturally, taking a single slap by Saitama produces very gory results. Cleanup on Aisle 4.
- Karmic Death: Mosquito Girl gets swatted by Saitama, leaving a bloody stain on the wall (although the "death" part is debatable; see A Twinkle in the Sky below).
- Mosquito Miscreants: A humanoid, Ax-Crazy mosquito.
- Ms. Fanservice: As stated above, she is an attractive woman with mosquito features in the manga. In the anime she also gets various shots of her body and has a sensual voice.
- Nightmare Face: The flash of her face as she started transforming in the anime was of her making a giddy Evil Laugh with glowing red eyes while drawn in shaking pencil lines.
- One-Winged Angel: After injecting herself with blood, she become much faster and powerful.
- Paint the Town Red: In the manga, she's just swatted through a building. In the anime, her blood-engorged abdomen messily explodes, leaving a large smear on the side of the building. The DVD version (which is also the Adult Swim one) had her both splatter her abdomen on the building and getting swatted through the building.
- Shameless Fanservice Girl: She doesn't seem to mind that Genos sees her nude, or if anyone else would be around the city as she raids it. But then again, being part insect provides some degree of exoskeletal modesty.
- She's Got Legs: And Genos takes care of them. She gets better, after absorbing blood.
- Super Mode: After absorbing enough blood, she Turns Red, regenerates her legs and becomes so fast that not even Genos, who fought her on even footing before, could keep up with her.
- Super Prototype: Said to be just a prototype, despite being the second strongest monster of the House of Evolution after the transformation.
- The Swarm: A large mosquito swarm, which she uses to drain animals and people and absorb their blood.
- A Twinkle in the Sky: It's blink-and-you-miss-it, but a humanoid form can be seen right after Saitama's swat sends her hitting a building in all three media forms. Some fans base themselves on this to argue that she may have survived after all.
- Vampiric Draining: The blood that her mosquitoes suck is used to increase her own power, given that she herself is a mosquito person.
Voiced by: Unshō Ishizuka (Japanese), Mike McFarland (English), Miguel Angel Ghigliazza (Latin American Spanish)
Debut: Chapter 9 (Webcomic & Manga), Episode 3 (Anime)
Disaster Level: Dragon
The pinnacle of Dr. Genus' efforts to create a physically perfect specimen - however, his mental state is unhinged and insane. He is easily the strongest being in the House of Evolution.
- Alien Blood: His blood is phosphorous green.
- Aura Vision: He is capable of visualizing Saitama's power as an overwhelming aura.
- Ax-Crazy: Extremely unstable. He is very intelligent, but has an insatiable blood lust and thus had to be locked up because he kept killing anything that got near him.
- Back from the Dead: Him or a clone of him is brought back to help train Zombie Man. Since Dr. Genus is okay with being in the room when this one is fighting, he seems to have this version under more control or fixed the insanity issue.
- Dub Name Change: The official translation refers to him as Carnage Kabuto, and he enters "Carnage" mode instead of "Asura" mode. Happens again in the Latin American dub, where he is called Asura Kabuto and the name of his second form is restored to "Asura mode".
- Evil Sounds Deep: Part and parcel when the one providing the voice is Unshō Ishizuka.
- Freak Out: Has a minor one when he realizes Saitama is much, much stronger than he thought.
- Genius Bruiser: Despite his arrogance and violent temperament, he's actually very intelligent and observant. He immediately realizes how strong Saitama is when he attempts to attack him.
- Gone Horribly Right: The pinnacle of the House of Evolution's experiments, but has to be chained in the basement because of his madness.
- Hoist by His Own Petard: By accident. His Carnage Mode lasts for a week... but he mentions that it'll last "until next Saturday". Saitama realizes that means today is Saturday, which means he's missing bargain day at the local supermarket, motivation enough to reduce Carnage Kabuto to a smear.
- Lightning Bruiser: Enough to beat Genos to a pulp.
- Nonindicative Name: Aside from the horn, his body isn't really based on rhinoceros. Rather, it's more like a rhinoceros beetle (''kabutomushi" in Japanese). The official translation even calls him "Carnage Kabuto" instead.
- Overly Long Tongue: In the anime. And he likes to remind the audience of it.
- Shout-Out: The green Tron Lines that it gains in the anime, along with its horn and purple skin during Asura Mode, make it look like EVA-01.
- Spider-Sense: He could sense just how dangerous Saitama is.
- Super Breath: Capable of reflecting Genos' incinerator back at him.
- Super Mode: Asura Mode. Of course against Saitama it doesn't help much, and he gets killed in one hit.
- Super Strength: He boasts a great amount of strength seen as how he was able to badly damage Genos with minimal effort in his base form.
- Super Speed: Despite his enormous size he boasts an exceptional amount of speed that he uses to attack his enemies before they can even react.
- Super Toughness: Completely unfazed from Geno's blasts or punches.
- Ultimate Lifeform: He was created to be this and certainly quite the Genius Bruiser. Also utterly insane and thus deemed a failure.
- Underestimating Badassery: Double Subverted. He freaks out upon realizing Saitama's stronger than he expected, but upon hearing about how Saitama got so strong, his disbelief and anger causes him to discard his assessment and use Asura Mode to attack. He should have stuck with it.
- Unstoppable Rage: The effect of his Asura Mode, declared to last an entire week. Leads to his undoing in a roundabout fashion.
- With Great Power Comes Great Insanity: He is the most powerful creation of the House of Evolution, but is too sadistic and unhinged to be of any real use. This gets him locked in chains in the basement, until he is released to face Saitama.
Voiced by: Jiro Saito (Japanese), Paul St. Peter (English), Dan Osorio (Latin American Spanish)
Debut: Chapter 8 (Webcomic & Manga), Episode 2 (Anime)
Disaster Level: Demon
The second-most powerful creation of the House of Evolution, and the leader of their strike force.
- Absurdly Sharp Claws: Sharp enough to slice entire buildings to pieces.
- Affably Evil: He politely waits when Saitama needed to shake dirt out of his pants.
- Bad Boss: Doesn't hesitate to slice weaker allies to pieces if they are in his way."Such is the law of the jungle!"
- Calling Your Attacks: "LION SLASH!" "METEOR POWER SHOWER!!"
- Casting Gag: According to Paul St. Peter, he was cast because the voice director of One Punch Man's English dub knew he had voiced Leomon previously, and wanted him specifically.
- Expy: Of Leomon from Digimon who was also a bipedal lion with a similar color scheme. In fact Leomon was also known as "The Beast King", which comes from his "Fist of the Beast King" attack Beast King's "Lion Slash" seems to be referencing visually. It doubles up in the English version, where his voice actor did voice Leomon too.
- Eye Scream: Threatened to claw Saitama's eyes out. In the end, Saitama ended up waving his dismembered eyeball as a trophy.
- King of Beasts: A human-lion hybrid, although he is only the second most powerful member of the House of Evolution, not the most powerful. But, even though he is not more powerful than Carnage Kabuto, Beast King's status as the second most powerful member of the House of Evolution and Carnage Kabuto's status as a failure, this would mean he is the most successful experiment produced by the organization.
- Ludicrous Gibs: What Saitama's Consecutive Normal Punches reduce him to.
- No Kill Like Overkill: Beast King is the second strongest fighter of the House of Evolution. He got killed when Saitama used Consecutive Normal Punches. Saitama took out the strongest fighter, Carnage Kabuto, with just one normal punch.
- Smug Super: Somewhat understandably self-confident, due to his high power level.
Voiced by: Shota Yamamoto (Japanese), Kaiji Tang (English), David Camarillo (Latin American Spanish)
Debut: Chapter 7 (Webcomic), Chapter 8 (Manga), Episode 2 (Anime)
Disaster Level: Demon
A cyborg gorilla created by Dr. Genus. He is notably more sane than the rest of the House of Evolution, even surviving the conflict to live a peaceful life at Dr. Genus' takoyaki stand.
- Adaptation Expansion: Is spared by Saitama, but never shows up again. In the anime, it is revealed he works with Genus in his takoyaki stand. He reappears in the manga when Zombieman finds him and Genus.
- Bad "Bad Acting": Being legitimately threatened with death while mostly dismembered and shown the eyeball of the monster one rank above him in strength in his organization caused him to instantly drop his unflinching robotic persona and go into a state of panic. And then he got yelled at by Saitama for dipping back into the performance while providing an overly-long Infodump on the House of Evolution and its creator.
- Curb-Stomp Battle:
- Gets quickly beaten by Genos in one of the battles where he doesn't lose a limb.
- In manga Chapter 78 though, he pulls this on Marshall Gorilla, an up-and-coming Tiger-class Monster that wanted to be promoted to Demon, beating him in one punch while out for groceries and having no understanding of what was going on or why, not unlike Saitama.
- Cyborg: He's the only combat cyborg in the House of Evolution.
- Exactly What It Says on the Tin: Well most monsters in the House of Evolution are like this, but he is well, essentially a gorilla in an armor.
- HeelFace Turn: Reappears alongside Genus in episode 11 of the anime, with the two of them cooking takoyaki and watching the events of the Alien Invasion on TV.
- Killer Gorilla: A cyborg gorilla that starts off as a villain.
- Know When to Fold Them: After Saitama shows him the lone remain of Beast King, he quickly gives up and begs to be spared.
- Overshadowed by Awesome: While he was defeated by Genos, it bears repeating that Genos was and is S Class in power. Best exemplified in his "battle" with Marshall Gorilla, a monster who took down an A Class hero with ease, where Armoured Gorilla killed him with one punch.
- Robo Speak: He's just faking it because he thinks it sounds cool.
- Sole Survivor: He's the only monster of the House of Evolution to actually survive, surrendering to Saitama after seeing him hold Beast King's eyeball.Armored Gorilla: "Umm...I'm sorry, I'll answer all your questions, so please spare my life."
Voiced by: Yoshiaki Hasegawa (JP), Kyle Hebert (EN)
Debut: Chapter 7 (Webcomic & Manga), Episode 2 (Anime)
Disaster Level: Tiger
A praying mantis-like mutant. He was the first to attempt to capture Saitama, and failed miserably.
- Alien Blood: He bleeds green.
- Curb-Stomp Battle: His "fight" against Saitama is over as fast as it started.
- Brain Monster: His brain is visible, as it's in a glass dome on his head.
- Evil Laugh: Has a brief laugh after breaking into Saitama's apartment.Kamakyuri : Heh heh heh heh !
- Informed Ability: According to Frog-Man, he's one of the strongest monsters of the House of Evolution. However, due to the brevity of his appearance, we don't get to see any evidence of this claim.
- Killed Mid-Sentence: He crashes through the roof of Saitama's apartment, tries to says his name, and Saitama kills him before he could finish that sentence.
- Off with His Head!: Saitama tears off his head from his body with a punch.
- Slaying Mantis: Looks like a humanoid mantis and is (supposedly) a dangerous monster.
- Spikes of Villainy: He has small spikes on his shoulders.
- There Was a Door: He enters Saitama's apartment by making a hole in the roof. Saitama doesn't take it very well...
- We Hardly Knew Ye: Gets killed in his third panel and he didn't get the chance to introduce himself.
Voiced by: Shinya Hamazoe (JP), Ben Diskin (EN)
Debut: Chapter 8 (Webcomic & Manga), Episode 2 (Anime)
Disaster Level: Tiger
A large mole-like mutant sent to retrieve Saitama.
- Inferred Survival: Since he became A Twinkle in the Sky instead of the usual splatter. However, the computer screen listed him as deceased so it's less likely.
- Mole Man: He's a talking humanoid mole (although he's more mole than man, and mostly looks like a giant mole).
- Oh, Crap!: Twice; first when Saitama lays eyes on him as the sole surviving monster among the group he was dealing with, leading to:
- Screw This, I'm Outta Here!: Made his exit by tunneling like a madman through the underground... but Saitama dove into the dirt and FOUND HIM...
- Tattooed Crook: He has kanji tattooed on his body.
- This Cannot Be!: His reaction to Saitama burrowing to find him
- Tunnel King: As a mole, this is naturally his primary ability. He's not good enough to escape from Saitama, though.
- You Have GOT to Be Kidding Me!: Has this reaction when he sees that Saitama managed to find him underground.
Voiced by: Hiroki Gotou (JP), Kirk Thornton (EN)
Debut: Chapter 7 (Webcomic), Chapter 7 (Manga), Episode 2 (Anime)
Disaster Level: Tiger
A frog mutant sent to retrieve Saitama.
- Curb-Stomp Battle: Gets defeated along with Slugrus by Saitama so quickly, Genos didn't even notice at first.
- Oh, Crap!: Looks rather distraught when he realizes Kamakyuri has been killed.
- Ludicrous Gibs: Surprisingly, it's not Saitama but Beast King who ends up killing both him and Slugrus in this way.
- Something Person: His name is "Frog-Man".
- Tattooed Crook: Has a tattoo on his shoulder.
- Those Two Guys: He seems to form a villainous duo with Slugrus.
- We Hardly Knew Ye: Appears only in a few panels before dying.
- Yank the Dog's Chain: Somehow, he and Slugrus managed to survive an attack from Saitama himself... only to be accidently killed by Beast King a few moments later.
Voiced by: Kenta Sasa (JP), Chris Cason (EN)
Debut: Chapter 7 (Webcomic), Chapter 7 (Manga), Episode 2 (Anime)
Disaster Level: Tiger
A slug mutant sent to retrieve Saitama.
- Curb-Stomp Battle: Gets defeated along with Frog-Man by Saitama so quickly, Genos didn't even notice at first.
- Eye on a Stalk: Being some sort of humanoid slug, he has a pair of long eyestalks.
- Ludicrous Gibs: Surprisingly, it's not Saitama but Beast King who ends up killing both him and Frog-Man in this way.
- Oh, Crap!: Looks rather distraught when he realizes Kamakyuri has been killed.
- Telepathy: Has some telepathic powers, allowing him to sense Kamakyuri's death.
- Those Two Guys: He seems to form a villainous duo with Frog-Man.
- We Hardly Knew Ye: Appears only in a few panels before dying.
- Yank the Dog's Chain: Somehow, he and Frog-Man managed to survive an attack from Saitama himself... only to be accidently killed by Beast King a few moments later.
- Bald of Evil: A defining trait of the Group is that every member has a clean shaved head. Saitama wasn't pleased when he heard about it.
- Curbstomp Battle: The whole Group was effortlessly slaughtered by Sonic and, while Hammerhead himself survived and even managed to put up a decent fight, he was still easily defeated.
- Empowered Badass Normal: They have no powers or abilities beyond that of a normal human, it all comes from their combat suits.
- Helmets Are Hardly Heroic: Admittedly, neither are they, but wearing helmets might have lead to less of them being decapitated by Sonic.
- Not-So-Well-Intentioned Extremist: Hammerhead and the rest of the group claim to be going about their destruction because they're rebelling against the corrupt elites of society, but in reality most of them (especially Hammerhead) simply don't want to have to work to get ahead in society.
- Off with His Head!: All of Hammerhead's henchmen by Sonic.
- Powered Armor: They use advanced combat suits to make up for their lack of powers.
Voiced by: Wataru Takagi (Japanese), Edward Bosco (English), Arturo Mercado Jr. (Latin American Spanish)
A charismatic brute who formed and leads The Paradisers. He survives the encounters with Saitama and Speed-'o-Sound Sonic, and later attempts to reintegrate into working society.
- Bald of Evil: He's not the nicest fellow around, and there's not a single hair on his head (nor on his whole body, as seen when Saitama destroys his armor, leaving him butt-naked).
- Born Lucky: He is born with a very, very thick skull, which saved his life when Sonic threw a kunai to the back of his head, and later when two agents of the Organization tried to kill him for stealing the battle suits in the first place.
- Brilliant, but Lazy: He managed to create a whole gang of devoted followers and outfit them with combat suits stolen from The Organization. His motivation for doing it? He just wants to remain unemployed and get paid for slacking off.
- Good Scars, Evil Scars: He has a large, horizontal scar across his nose.
- HeelFace Turn: After the events of Chapter 12/Episode 4, he gave up on terrorism and is actively looking for an honest job. Also, in Episode 11 is seen watching the events of the alien invasion on TV with his family, while filling in a job application.
- His Name Really Is "Barkeep": Hammerhead is indeed his actual name as it's what he uses to sign legal documents.
- Ineffectual Sympathetic Villain: Even Saitama seems to have a soft spot for him, and simply destroyed his armor and told him to run instead of gibbing him like most of the villains he usually deals with.
- In the Style of...: He looks like an Akira Toriyama character.
- Large and in Charge: He's over 7 feet tall, clearly towering over the rest of his henchmen.
- Large Ham: He's better at talking the talk than he is at walking the walk, that's for sure. It doesn't make him less of a threat, though.
- Not So Different: Saitama notes that like him, Hammerhead is a slacker by nature and wonders if he would have gone down a similar route.
- Powered Armor: Just like the rest of his Group, he wears an advanced battle suit to boost his physical strength to superhuman levels. The specific one he's wearing is an even more powerful variant, distinguished by unique flame decals emblazoned across its torso and thighs.
- Strawman Has a Point: Yes, having a job might not be as fun or exciting as it sounds. Yes, there are people starving out there because they're unemployed. But Hammerhead merely wants to slack off, and, given the nature of the manga, this guy is preaching in a city where most people are happy with their vocation and nobody is homeless.
- Strong Family Resemblance: He really wasn't kidding when he thanked his mother for his hard head: both his mother and grandmother share his unique skull-shape.
- The Big Guy: See Large and in Charge above.
- Unwitting Pawn: To the Organization, which let him steal their battle suits so he could test them in the field.
- Utopia Justifies the Means: Even if his "utopia" is just an excuse for lazy people like him to keep slacking off all day and still get paid for it.
- Well-Intentioned Extremist: Parodied. Hammerhead tries to invoke this trope, but it's hard to imagine a dumber, less practical goal.
Dark Matter Thieves
- Alien Invasion: They attack the planet Earth, and likely would've conquered it had it not been for the efforts of Saitama and the other heroes.
- Aliens Are Bastards: They have zero qualms about annihilating entire populated cities down to rubble.
- Ominous Floating Spaceship: They travel to Earth in one of these, which they then use to blow up most of City A.
- Space Pirates: They appear to be this, being a loose assortment of mercenaries and supervillains from different planets, attacking and pillaging their way across the universe. Boros outright refers to his forces as being a "pirate band".
Voiced by: Toshiyuki Morikawa (Japanese), Chris Jai Alex (English), Dafnis Fernández (Latin American Spanish)
Debut: Chapter 36 (Webcomic), Chapter 32 (Manga), Episode 10 (Anime)
Disaster Level: Above Dragon
A galactic ruler, who, just like Saitama, is extremely powerful and can defeat any opponent, but soon grew bored when he believed there was no one left worth fighting. When a seer informs him that someone could pose as a challenge to him on Earth, he travels there to battle this prophesied warrior.
- Affably Evil: He's nothing but polite to Saitama in their interactions. While he's supremely confident in his abilities he's also respectful to Saitama for being able to take what he can dish out, and graciously accepts his defeat. It's almost enough to make one forgot that he's a Galactic Conqueror who has laid waste to numerous planets, intended to do the same to Earth and attempted to destroy all life on the planet just to kill Saitama.
- Affectionate Parody: His character is almost entirely shout-outs to various Dragon Ball characters like Goku and Piccolo, so he's an Affectionate Parody of the series as a whole.
- Aliens Are Bastards: He orders his ship to level A-City completely. Why? Because it was there, and he had nothing better to do.
- Alas, Poor Villain: Despite Boros' murderous and imperialistic ways, Saitama can't help but relate to his struggle for fulfillment. Boros' life had been so empty until he faced Saitama in battle, but it ended up killing him anyways. Saitama departs the broken spacecraft with a solemn expression on his face, as if he begrudgingly respects the intergalactic menace.
- Ambiguous Situation: What actually killed Boros is subject to debate. Throughout the fight he's referring to the energy he's projecting as something similar to his own life force. Culminating in throwing all his energy into his final move, the Collapsing Star Roaring Cannon. While it's obvious that Saitama's "Serious Punch" did some damage, he was durable enough to survive it. It's possible that Boros may have been intending to kill himself just so he could secure the win.
- Anime Hair: To go with the DBZ parody, he has spiky hair with bangs that frame his face.
- Arc Villain: Of the Alien Conquerors arc.
- Aura Vision: He can literally see Saitama's power via an aura.
- Authority Equals Asskicking: He's the leader of the alien invaders and is naturally the strongest member.
- Bad Boss: He isn't seen abusing his underlings, but he also had no concern trashing his ship while fighting Saitama, even when his underlings were still on it.
- Battle Aura: Have you guessed he's the DBZ parody yet? It's so powerful that it destroys the area around him whenever he moves.
- Be Careful What You Wish For: He really wanted an exhilaratingly powerful opponent to fight, and he got one. Unlike most examples, he's not bothered by getting more than what he bargained for.
- Blood Knight: He really, really wants a good fight.
- Curbstomp Battle: Clearly capable of delivering these, as his character somewhat mimics a darker version of Saitama. Lampshaded by Boros himself in a melancholy sort of way while dying after a vicious one-sided battle against Saitama.Boros: You lie. You had strength to spare. I never stood a chance. It wasn't even a battle. So much for prophecies. You were too strong... Saitama...
- Cyclops: Only has one eye — on his face at least, see Eyes Do Not Belong There below.
- Dangerous Forbidden Technique: Meteoric Burst, a Super Mode that amps ups his already impressive strength and speed but at the cost of putting tremendous stress on his body similar to anaerobic exercise. He usually only uses it to finish fights quickly.
- Disc-One Final Boss: He's the last major enemy faced in the first season of the anime. And after his death in the manga and webcomic, no enemy except Awakened Garou gives the same level of performance.
- Evil Counterpart: To Saitama as he is basically "a villain for fun". Both of them are incredibly overpowered to the point where they lose interest in their later battles, and search for a Worthy Opponent. Saitama does that by being a hero for a hobby. As for Boros, Saitama put it best upon hearing his reason for attacking Earth...and punching him for it.Saitama: Are you stupid? You can't just go attacking other planets just to liven up your boring life. Even telemarketers wouldn't think of that.
- Explaining Your Power to the Enemy: Boros does this in a short break between his fight with Saitama, namely how he has the best Healing Factor out of all the species from his planet. He demonstrates this by regrowing the arm that Saitama managed to tear off.
- Expy: He's a mish-mash of various Dragon Ball characters. Mainly, he's got bits of Frieza (Evil Overlord, big battleship, Quirky Mini Boss Squad, restrictive forms, The Prophecy) combined with bits of Goku (Anime Hair, questing for a stronger opponent, a glowy Super Mode that makes his hair grow bigger and gets compared to anaerobic exercise) and Piccolo (big pointy ears and regenerating limbs). In the anime version his cape, baggy pants, and regenerating From a Single Cell are also reminiscent of Majin Buu's. Interestingly, he has also some traits in common with the later Dragon Ball villain Beerus, notably the prophecy which brought him to Earth to find a suitable opponent, destroying worlds for a hobby, and of course his similar name.
- Eye Beams: Shoots his energy blasts out of the eye on his chest.
- Eyes Do Not Belong There: A big eye on his chest.
- Face Death with Dignity: Accepts his loss against Saitama with dignity, having a civilized talk with the man about everything before dying, and acknowledging he never really had a chance against Saitama.
- Galactic Conqueror: He claims to be the ruler of many planets.
- Good Thing You Can Heal: Thanks to his regenerative powers, he survives multiple punches from Saitama.
- A Good Way to Die: How he feels about his loss against Saitama, since it was what he always wanted: a battle against a Worthy Opponent.
- Graceful Loser: He takes his defeat quite well since he got the challenging opponent he wanted.
- Healing Factor: Apparently has the best of his entire species. Because of it, he's the first villain to take multiple punches to kill, capped off with a Serious Series punch, and even then he lingers long enough to deliver a final speech before kicking it. He even manages to almost instantly pull himself together from a barrage that reduces everything but his eye to a thin red paste. It's even implied that the reason he died from the Serious Series punch was simply because he had used up all his energy firing off his final Wave-Motion Gun and didn't have any left to heal.
- Humanoid Abomination: At first, Boros looked more human and had a steel-plated looking armor with a skull-looking ornament. This humanoid form contains enough power to destroy a planet. His design was later changed by Yusuke Murata in order to look more alien.
- Invincible Villain: Not so much in the series itself, but he was alluded to being the final boss of ONE's earlier work "Sun Man" where he was far too powerful for the hero to defeat. Also deconstructed, as a lifetime of easy victories prior to meeting Saitama made him numb to any sense of accomplishment.
- Ironic Echo: At the height of his battle with Saitama, you can hear his heart beat in a way that mirrors Saitama's mole-people fantasy from the first episode.
- Kamehame Hadoken: His Collapsing Star Roaring Cannon, which fits in his being an Expy of Dragon Ball characters. He also has a weaker variant that vaporize whole cities.
- Knight of Cerebus: His entrance into the story shifts the light-hearted nature of the manga a little. Just a little, though. Oh, and he's the first villain to survive a normal punch from Saitama. Subverted when, as he lays dying, he accuses Saitama of not fighting seriously the whole time, although his arc still changes the mood of the story for the darker due to the sheer devastation it causes.
- Lightning Bruiser: The strongest opponent Saitama had faced at that point, strong enough to kick Saitama to the Moon and fast enough that the shockwaves from moving around were wrecking his ship, and durable enough to survive an extended fight with Saitama's Normal Series.
- Mr. Fanservice: He is very muscular, attractive despite being a Humanoid Alien and gets a lot of chest and lower back shots due to technically fighting in the buff.
- Not So Different: He's a powerful being who, after becoming the strongest being in his home planet, fell into a depression because there was no one left worth fighting.
- Omnicidal Maniac: He destroyed most things in the galaxy all because he was bored of not having a Worthy Opponent and attempted to destroy the Earth all so he could beat Saitama.
- Person of Mass Destruction: He does more unintentional damage to his own city-sized spaceship while fighting Saitama than everything the S-Class heroes hurl at it deliberately. He also claims his ultimate attack could wipe out all life on the Earth's surface.
- Power Makes Your Hair Grow: In Meteoric Burst, making him look like a Super Saiyan 3.
- Powered Armor: His armor channels the powers he was born with, and also acts as a Power Limiter. Destroying it—which Saitama does with his first blow — just makes his power go out of control, energy wise.
- The Prophecy: The entire reason he came to Earth? Some alien prophet predicted there'd be a worthy equal to be his opponent for him there. He finds his opponent alright, but Saitama is in his own league. But Boros doesn't mind, because he got the duel he dreamed of.
- Pulling Themselves Together: He gets punched into an eye and a smear of blood, thanks to Saitama's Consecutive Punch Combo, and manages to pull off this trope by sheer strength of will.
- Rubber-Forehead Aliens: Ironically the only non-human things about his looks are his blue skin, pointy ears, sharp teeth, and single cyclops-like eye.
- Super Mode: His "Meteoric Burst" form. It is Boros' trump card which he resorts to when he wishes to settle a fight quickly. He uses his latent energy to boost his body to speed and power beyond its limit, at the cost of putting immense burden on his body and even shortening his lifespan. This also completely changes his appearance.
- Super Speed: Boros has immeasurable speed and agility, as he was able to keep up with a casual Saitama. He uses the latent energy shunted from his body as a means of propulsion, making him so fast to the point that his path of movement often zig-zags, and anything he touches while moving at this speed instantly evaporates.
- Super Strength: Boros displays extreme amounts of strength during his fight against Saitama. He was also able to knock Saitama through several massive pillars within his throne room with only one punch, the alien's various strikes easily damaging the place. And then there's the fact he kicked Saitama to the moon hard enough to leave a crater on impact.
- Super Toughness: Boros is shown to be amazingly resilient, to the point of being the first opponent of Saitama to survive, after being hit directly by his punch, despite having his full powers sealed by his armor. After releasing his power, another punch from Saitama only tore off his arm, and he was barely inconvenienced by it. And in Meteoric Burst, a direct punch to his chest causes Blood from the Mouth and sends him flying and stumbling to get up, but the fact remains he's still in one piece. It takes Consectutive Normal Punches in order to finally be reduced to Ludicrous Gibs.
- Superpower Lottery: Boros was gifted with superpowers since the beginning and vastly increased his powers with time and experience. He claims that he in particular, possesses regeneration, physical ability and latent energy that far surpasses others, including members of his race.
- Volcanic Veins: Appears on him when his power-limiting armor is broken, letting his immense energy run loose. He then gets what amounts to a "color-inverted" version when he uses Meteoric Burst, along with a Power Up Full Color Change — that is, the parts of his body that used to be dark and non-glowing are now glowing a bright white, while the formerly glowing veins now seem to be glaringly dark in comparison. Here's how the end result of Meteoric Burst looks.
- Victory Is Boring: The entire reason he became a galactic conqueror was in the hopes that one day, he'd find an enemy worth fighting.
- Villain Respect: Boros is so far, the only villain who actually took Saitama very seriously, knowing just how strong he was with a single glance. He is also the only villain who gives massive respect to Saitama, viewing him as a Worthy Opponent. Even when he loses, Boros doesn't mind because Saitama gave him the exciting fight he always wanted.
- Villainous Valor: During the later part of his fight against Saitama even when it becomes clear that all of his attacks up until this point have done no damage, he continues to use Meteoric Burst despite the massive strain it puts on his body, and even after he gets pulverized completely he pulls himself back together with visible effort and defiantly declares that he will defeat Saitama while preparing his ultimate attack for one last stand despite all the damage he's taken so far.
- Wave-Motion Gun: His Collapsing Star Roaring Cannon, which channels all his energy into a planet-killing beam, though the exact specifics of it vary: the manga states this attack would scorch the planet's surface of all life, while the anime has him state it would blast the whole planet itself to hell.
- World's Strongest Man: One of the two strongest non-Saitama character in the series, with strength, speed, durability, and energy projection several orders of magnitude above the strongest S-Class heroes and Dragon-class monsters; with the other being Awakened Garou. Much like Frieza from Dragon Ball Z, he doesn't appear to have ever had to train or work for his power. Boros is as strong as he is naturally and actually has to suppress his true strength so that he doesn't die from overexertion.
- The Worf Barrage:
- He immediately proves how he's on a completely different level compared to the previous antagonists in the series when he gets back up after getting punched by Saitama. It's a downplayed example though since he still took quite a bit of damage from it.
- He's later on the giving end of a Worf Barrage when his ultimate attack, Collapsing Star Roaring Cannon, is blown away by Saitama's Serious Series: Serious Strike.
- Worthy Opponent: He seeks this, and Saitama pretends to treat him as one - Saitama tries to comfort him as he dies, mourns over his last breath, and in the anime expresses disgust when he fights a Dragon level threat the next day that can't also No-Sell his typical One-Hit Kill. Saitama purposely gave Boros an exciting fight, because he sympathized with him and knew exactly what it felt like to be so powerful that nothing is exciting anymore. But it turns out to be a subversion; as he dies he admits he knew Saitama was holding back and wasn't fighting seriously the entire time. That said, Saitama does acknowledge him as his strongest foe.
Voiced by: Kōki Uchiyama (Japanese), Vic Mignogna (anime), Kellen Goff (A Hero Nobody Knows) (English), Jorge Ornelas (Latin American Spanish)
Debut: Chapter 34 (Webcomic), Chapter 31 (Manga), Episode 10 (Anime)
Disaster Level: Dragon
One of Boros' three generals. He is a shapeshifting and regenerating alien with five separate personalities shared in one body. He gave four S-Class heroes some trouble and dismembered Iaian, but was nevertheless defeated.
- Achilles' Heel: Each head has a small marble-like brain which allows them to regenerate endlessly. If a marble is destroyed, the associated head melts instantly, and Melzargard dies once they're all destroyed. This is mitigated somewhat by the fact that he has multiple heads and can freely move his brains within his body. However, his regeneration always begins with his heads, meaning that the brain can be easily found if his body is completely destroyed and forced to regenerate from scratch.
- Catchphrase: "That is good!".
- From a Single Cell: He can be reduced to a pile of chunks, but as long as his brains survive he can rebuild himself in seconds.
- Hypocrite: He constantly insults the Heroes for being fragile targets, ignoring the fact he would have been killed instantly by an A-Rank Hero if not for his regenerating abilities.
- Lovecraftian Superpower: He can freely control the shape of his body, from separating into one body for each head, merging all of his heads and bodies into a single form, and shapeshifting his limbs into any weapon he needs.
- Multiple Head Case: Each head possesses a different personality and speech pattern. One speaks in broken, simplistic language; another is analytic of things happening around Melzargard; another one is violent and suggests killing everything; one only praises the other heads by saying their ideas are good; and the final one seems to be in charge, taking action based on what the others say. It should be noted that the fewer heads Melzargard has, the more developed its speech patterns are.
- Nightmare Face: With all five heads combined, it has stacked pairs of eyes and multiple layers of teeth.
- Oh, Crap!: Gets an amazing one when Metal Bat grabs one of his brains.
- Shapeshifter Weapon: He can form all kinds of weapons, including axes, hammers, spikes or just a mass of tendrils.
- Smug Snake: Repeatedly taunts the S-Class heroes on how their attacks are useless due to his regeneration, only to slowly lose control of the fight once they figure out his weakness. He later claims that the S-Class heroes would die instantly if he focused solely on attacking them, only to be shocked to find that Bang wasn't hurt from his attack. It's also noticeable that he only lands two hits on his whole fight (one on Ia-Ian and one on Silverfang), and the latter doesn't even do any actual damage: despite his claims about his strength, he's only able to get beaten over and over again by the heroes until they find a way to kill him.
- Unskilled, but Strong: What's mainly dangerous about him is his incredible attack power and how his regeneration allows him to shrug off most attacks.
- Villainous Breakdown: With each head he lost, he lost his head some more, going from a Creepy Monotone to a rambling and cackling lunatic.
Voiced by: Shinya Hamazoe (Japanese), Bill Rogers (English)
Debut: Chapter 36 (Webcomic), Chapter 32 (Manga), Episode 10 (Anime)
Disaster Level: Dragon
- Acid Attack: He has acidic breath, although he does not get a chance to demonstrate this before Saitama literally knocks his block off.
- Elite Mook: According to Geryuganshoop, he was the top fighter in Boros' army. However, given that he was unlucky enough to run into Saitama, we don't know what he really is capable of.
- Eyeless Face: It's just one big mouth.
- Hollywood Acid: His breath which he claims can melt anything.
- Killed Mid-Sentence: Has his head punched off by Saitama while he was in the middle of bragging about his acid breath.
- Lost in Translation: His Japanese name "Guroribāsu" is a portmanteau of "guro" (meaning gross) and "reverse" (meaning to vomit), meaning his name should be Guroreverse. That name is pretty mouthy for English speakers, so they just left out the pun in translation.
- Smug Snake: He gets pulverized by Saitama just as he was bragging about how powerful he is.
- We Hardly Knew Ye: When you run into Saitama it tends to happen.
- Xenomorph Xerox: He's an alien with an Eyeless Face, More Teeth than the Osmond Family and additional mouths who can emit acid, all of which are very reminiscent of the Xenomorph.
Voiced by: Hiroki Gotou (Japanese), Brian Beacock (English), Emmanuel Bernal (Latin American Spanish)
Debut: Chapter 36 (Webcomic), Chapter 32 (Manga), Episode 11 (Anime)
Disaster Level: Dragon
One of Boros' three generals. He is a telepathic and telekinetic alien in charge of the spacecraft's controls.
- Bad Boss: Saitama is not affected by his gravity warping in any way, but we do see a couple of unfortunate mooks that happened to be within range get squished like pancakes, showing that Shoop is not all talk. And that he doesn't particularly care about his allies.
- Boom, Headshot!: How he dies. Saitama flicks a rock through his head.
- Death by Irony: He attacks Saitama by telekinetically hurling lots and lots of rocks at him, to no effect. Saitama kills him by tossing just one rock at him.
- Gravity Master: Using his telekinesis, he can increase the force of gravity. This would have been impressive if his opponent were anyone but Saitama, who isn't even affected by it.
- Mission Control: Seems to be his role on the alien ship.
- Mind over Matter: Claims to be the most powerful telekinetic in the universe.
- Octopoid Aliens: Saitama even confuses Geryuganshoop for a literal octopus upon first sight of him.
- Oh, Crap!: Continually as every attempt to stop Saitama fails. Has a more comical one when Saitama trolls him by saying he's lost and then going in the opposite directions Geryuganshoop gives him.
- Squishy Wizard: He is very good at annihilating most opponents before they can get into melee range, but a simple pebble splits his head in twain. It should be noted that the pebble was thrown by Saitama, but it still gives off this impression.
- Smug Snake: Calls himself the greatest telekinetic in the universe. Saitama is unimpressed, though, and his shown feats are not even on level with those displayed by Tornado of Terror (admittedly, he may be holding back to avoid at least obliterating his own ship if not his allies).
Monster AssociationSee Characters.One Punch Man Monster Association.
- Bond Villain Stupidity: They don't bother to check if Hammerhead is really dead, which allowed him to survive.
- Brain Monster: One of them has his brain stored in a glass dome on his head.
- Cyber Cyclops: One of them is a robot that seems to only have one red eye.
- Killer Robot: What they seem to be. They fail to kill Hammerhead though, but they don't know that.
- Out-Gambitted: As it turns out, Hammerhead stealing and using their combat suits was part of their plans all along. In reality, they deliberately allowed him to do so because they wanted to collect real battle data.
- No Name Given: For now at least, we were not given any names for them.
- Those Two Guys: A pair of villainous robots that appears to work as a duo.
- You Have Outlived Your Usefulness: They only let Hammerhead alive after he stole their combat suits so he can test those for them. After his defeat and the destruction of the suits, they come to kill him since he's no longer useful to them. Unbeknown to them, he actually survives their attack.
Voiced by: Tarō Kiuchi (Japanese), Chris Tergliafera (English)
Debut: Chapter 42 (Webcomic), Chapter 37 (Manga)
Disaster Level: Demon
A giant knight robot from the "Machine God" series, sent by the Organization to test King's combat ability.
- Adaptation Name Change: Was named "Zsimov" in the original webcomic.
- Beam Spam: G4's true form does this to Genos in their fight.
- BFS: Wields a massive sword that can be retracted from its giant chakra wheel on its back.
- Cyber Cyclops: Its Mecha form has a single eye.
- Mecha: It turns out to be a small robot piloting a large mecha.
- Requisite Royal Regalia: It wears a fur cape, has a giant crown and is decorated with shiny ornaments.
- Sadistic Choice: It gives King an ultimatum; if he does not fight, it will kill 10 civilians each minute.
Debut: Chapter 128 (Webcomic)
Disaster Level: Dragon
The village was first founded by the unnamed "Ninja Village Leader", but it is no longer in operation thanks to Flashy Flash's purge.
- Always Male: According to Flashy Flash, all of the members are male.
- Driven to Suicide: The Ninja Village defies this for the trainees, if they attempt to do this to free themselves from the hellish training, through the specialized medicine they injected into them.
- The Insomniac: As part of the training curriculum, a day for them consists of 72 hours while only getting 6 hours of sleep.
Ninja Village Leader
The unnamed founder of the secret Ninja Village.
- Asskicking Equals Authority: The strongest and deadly ninja known to the world, and is the founder of the Ninja Village that puts children through hellish training to become assassins.
- Body Horror: Due to his interest in grafting the bodily remains of his fallen enemies onto his own body, his own appearance is monstrous as seen in the page image.
- Expy: Considering the hidden Ninja Village he was running was inspired by Naruto, the Ninja Village Leader has similarities to two villains from the franchise, such as Orochimaru (being the founder of a hidden Ninja Village) and Kakuzu (grafting body parts of his enemies onto his own to grow stronger).
- No Name Given: He is never referred by name, the most consistent way others refer to him is simply by "That Man".
- Really 700 Years Old: He was born over 300 years prior to the series, as he was capable of longevity through the constant body grafting of his enemies.
- Worf Effect: 15 years prior to the story, he was rendered in a coma from Blast, showing that not even the Ninja Village Leader's own immense power and skill is enough to match him; and after all the build up from his return, even remarking that he is stronger than ever before, the guy cant even amount to an actual on-panel fight for Saitama in the webcomic, he is dealt with completely off panel, in the end he was used as a means to an end: giving Flash and Sonic new abilities through getting his weapons and scrolls.
- World's Best Warrior: He was regarded as the most powerful ninja to walk the Earth.