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 super speed who hires himself as a freelance assassin. After a humiliating defeat by Saitama, Sonic declares himself his unofficial nemesis and hounds him for the opportunity to avenge his defeat.
- Affably Evil: In the third OVA when he gets A Day in the Limelight. When he's off the job he's an all round 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 up on 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 get 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.
Voiced by: Toshiki Masuda (Japanese), Todd Haberkorn (English), Miguel Ángel Leal (Latin American Spanish)
Bang's only disciple. Quite the braggart. He was "expelled" by his master for his lack of skill at martial arts, only to realize it was for his sake to keep him away from encountering Garou. Unfortunately, he ignored Bang's secret warning and ended up being beaten by his former fellow disciple.
- Butt-Monkey: He is so insignificant that Saitama initially has difficulty remembering who is.
- Curb-Stomp Battle: Charanko is a worse than average martial artist living in a world of monsters and superheroes, leading to him being on the receiving end of these quite often.
- Doomed Moral Victor: Despite everyone telling him (and perhaps Charanko even realizing) that Garou is too dangerous to mess with and that Charanko is too weak to ever match him in a fight he does it anyway to defend his master's honor. Saitama even mentions to a former disciple of Bang's that Charanko was way stronger than the former disciple (who was second only to Garou in the dojo) because Charanko didn't run, and indeed faced Garou head on.
- Honor Before Reason: He attacks Garou head on even after Bang makes it clear that doing so would end in disaster. It doesn't end well.
- Hot-Blooded: When his master is insulted, he immediately and loudly challenges Genos in a duel, despite Genos being a known S-class hero.
- Overly Narrow Superlative: Was originally the lowest ranking member of Bang's dojo, which was also pretty much what saved him from being trashed by Garou, and subsequently became the top ranked disciple by virtue of being the only one left.
- Small Name, Big Ego: He thought he could take Genos and Saitama in a fight. Genos proved him otherwise.
Voiced by: Kenichi Ogata (Japanese), Doug Stone (English), Jaime Vega (Latin American Spanish)
The scientist who saved Genos 4 years ago by turning him into a cyborg.
- Almighty Janitor: Despite being the reason Genos can blast apart mountainsides and why he instantly became an S-Class hero, Doctor Kuseno is only seen using his skills to provide Genos with repairs and upgrades.
- Early-Bird Cameo: Appeared in Episode 4 fixing up Genos and created the arms that Genos used in the sparring match with Saitama.
- Gadgeteer Genius: He is a by far the most skilled inventor along with Child Emperor. He can build parts for Genos to blow a whole building away!
- Improbable Hairstyle: He has a bowl-cut that looks more like a mushroom cap.
- Nice Guy: Saitama considers him this after hearing how he gave Genos the ability to taste and convert food to bio-fuel so he can still eat despite being mostly mechanical.
- Parental Substitute: He is a father figure to Genos, expressing concern for him. He always reminds him of not being reckless all the time and that they are together in their battle.
- Science Hero: Genos refers to him as the 'Doctor of Justice'.
- Unfortunate Names: While his name has no direct translation, Kuseno is an impolite form of kusai, which means Stench.
Voiced by: Shinya Fukumatsu (Japanese), Brook Chalmers (English)
Bang's older brother. A martial artist who is also the Master of the Whirlwind Iron Cutting Fist Style.
- Back-to-Back Badasses: When he teams up with his brother, Bang.
- Badass Beard: In contrast with his brother who has a Badass Mustache.
- Bald of Awesome: While his brother Bang still has his hair, Bomb is bald.
- Bare-Fisted Monk: Like his younger brother, he also uses martial arts in fighting.
- Blow You Away: His martial art style, "Whirlwind Iron Cutting Fist Style" involves manipulating the air to create Razor Wind and blow his enemies back with tremendous force.
- Cool Big Bro: Despite in their old age, he still shows care towards his younger brother Bang.
- Cool Old Guy: He's Bang's older brother and he's willing to close down his dojo to help his brother deal with Garou.
- Fantastic Fighting Style: The "Whirlwind Iron Cutting Fist Style".
- Feeling Their Age: He often complains about being too old to be active anymore when hunting down Garou with Bang.
- Old Master: He's older than his brother, who is 81. While not much known is about Bomb's strength; ONE stated that he's stronger than Bang, and it is safe to say that his strength is on par with the S-Class heroes.
- Razor-Sharp Hand: Is capable of cutting through mysterious beings with his bare hands thanks to his martial art techniques.
- Razor Wind: His "Whirlwind Iron Cutting Fist" allows him to generate concentric rings of pressurized air that cuts through opponents.
- Supernatural Martial Arts: Much like his brother, he has his own martial arts, the Whirlwind Iron Cutting Fist Style. Despite being even older than Bang, thus style allows him to fight on equal rank with his younger brother.
Voiced by: Ayumi Mano (Japanese), Jackie Lastra (English)
Metal Bat's younger sister. First appears in Murata's redraw.
- Badass Adorable: Despite being a little girl she stands up to Garou and tells him to leave big brother Metal Bat alone, because he promised to take her to her recital. She then slaps her brother so hard that he passes out though he had already been severely beaten.
- Badass Normal: For essentially taking her life in her hands by stepping between Garou and Metal Bat. She had no way of knowing whether Garou would respect her rules, but it was all she had to protect her brother with.
- Big Damn Heroes: Steps in between Garou and her brother during their fight. Though considering how the fight was going it's unclear who she was preventing from getting killed.
- Canon Foreigner: A god-created one — the arc she first appears in is only in the redraw, but the story's still credited to ONE and she had been mentioned in the webcomic long before this.
- Fangirl: She is one of Sweet Mask. She was annoyed that her brother used his S-Class promotion request for an unbreakable bat rather than for his autograph.
- Morality Pet: Metal Bat's not a bad guy, but he'd be more of a Jerkass if it weren't for her, not to mention more recklessly hot-blooded.
- Nice Girl: Seems quite friendly, if a smidge overbearing.
- No Hero to His Valet: She tends to scold Metal Bat for things like missing her piano recital when his hero work gets in the way. Word of God is that she's not the kind to brag to other schoolkids about her brother being an S-Class hero.
- Not in Front of the Kid: Invoked. Metal Bat promised not to fight in front of her, which she uses to break up his fights when she's nearby.
- Tsurime Eyes: And quite justified, given her first appearance sees her standing up to Garou. (It helps that they're similar to her brother's, giving her "delinquent eyes" despite being very girly in appearance otherwise.)
Voiced by: Natsumi Fujiwara (Japanese), Jeannie Tirado (English)
A young child that loves heroes and who Garou occasionally talks to.
- Badass and Child Duo: Occasionally forms with Garou, being the "Child" to Garou's "Badass".
- Big Ol' Unibrow: To add on to his Gonk appearance.
- Fanboy: Of the Hero Association.
- Gonk: He's not exactly cute for a kid, something that Garou lampshades.
- The Load: In Chapters 81 and 82, Garou would have had an easier time fighting off the eight heroes that were sent after him had he not been trying to protect Tareo from being collateral damage in the fight, as the eight heroes were unaware that Tareo was hiding close by.
- Morality Pet: He is pretty much there to show that Garou isn't completely a bad person. Garou is even forced to save him sometimes from being collateral damage by the heroes hunting Garou down and from members of the Monster Association.
- Only Friend: Perhaps the only one closest to being Garou's friend.
- Unwitting Instigator of Doom: The hero catalog he carries around has given a lot of intel to Garou on how to track down heroes and finding their weaknesses.
Voiced by: Ayaka Shimizu (Japanese), Morgan Berry (English)
The son of Narinki, an executive of the Hero Association. His kidnapping spurs the S-Class heroes into taking down the Monster Association.
- All Take and No Give: As mentioned in Ungrateful Bastard below.
- Badass and Child Duo: With Child Emperor. They're both admittedly children, but Child Emperor is the prodigy hero while he's just dead weight.
- Complaining About Rescues They Don't Like: Despite the heroes putting their lives on the line to save him, the moment they take damage or run into trouble, he'll whine and insult them to do better.
- Dirty Coward: He brags and talks tough when things look to go his way during fights between heroes and monsters, but when they don't, boy is he quick to cry and grovel for the monsters to spare him. Even literarily pisses his pants when all the surface team heroes are defeated by Nyan, and he realizes he's unable to escape.
- It's All About Me: Because his father is one of the main financial investors, he thinks the Hero Association exists to cater to his every need and whim. He even refers to it being "his" Association during a fight.
- Jerkass: He's a Spoiled Brat who seems to think it's a privilege for others to do things for him and can't spare a moment of thanks when they help him or save him.
- Meaningful Name/Punny Name: "Waganma" is a play of words of "Wagamama", which means "spoiled".
- Spoiled Brat: Oh yeah. It's even in his name.
- Ungrateful Bastard: Let us count the ways...
- Takes Tareo's only piece of food without thanking him, then declares him 'useless' for not having more.
- Admonishes Child Emperor for not coming to his rescue quickly enough, though a glare from Child Emperor is enough to shut him up quickly.
- Constantly insults Child Emperor during his fights.
- Intentionally lies to Child Emperor about Tareo being imprisoned as well, thinking of his own safety. Naturally once he's exposed via Atomic Samurai mentioning seeing Tareo, he gets a Death Glare from Child Emperor for this before heading back underground to assist the other heroes in exterminating the remaining monsters.
- This is later revised into him admitting the truth to the gathered heroes and apologizing for lying. Child Emperor now thanks him for telling the truth.
Voiced by: Taro Yamaguchi (Japanese), Bill Butts (English)
A martial artist and user of the Dark Hell Assassination. He is said to be a top contender in the martial arts tournament.
- Arrogant Kung-Fu Guy: He is extremely arrogant during battle since he states that all contestants in the Super Fight Tournament are a bunch of weaklings. Bonus point for being a martial artist. He eats a bunch of monster cells all at once with the intent of becoming the strongest monster alive, even after Gouketsu tells him not to, and all it gets him is his death... until it turns out he did survive and became potentially a Dragon-level threat.
- Berserk Button: Fellow martial artists who treat the tournament as sparring and competition. He becomes irate when Saitama does not take on a stance, believing him to be untrained and an insult to fight.
- Blood Knight: He is quite bloodthirsty, wanting to kill Suiryu. He proves it again when detailing how he will hurt Saitama with a smile on his face.
- The Brute: Bakuzan is a muscular built man with spiky, dark hair. He is excessively brutal towards his opponents, especially those he feels are not worthy of facing him. Up to Eleven after his transformation into a monster.
- The Bully: After becoming a monster, he admits to himself that the only reason why he wanted strength was to pick on those weaker than him. He proves it by torturing a half dead Suiryu.
- Even before his monsterization, he was this, thrashing his opponents so badly that the referee and medics had to be on immediate standby to call the match and get his opponent medical attention because of how quickly he could, and would, inflict potentially-lethal injuries in a tournament fight. Becoming a monster merely makes him willing to admit this outright.
- Curb-Stomp Battle: When Saitama asks for a demonstration of his strength, Bakuzan agrees to comply, detailing exactly how he intends to defeat Saitama, in a brutal, exceedingly cruel fashion. However, he touches Saitama's head and nearly knocks over his wig, causing Saitama to punch him into the air in panic.
- When he transforms into a monster, he doesn't hesitate to land one on Suiryu (weakened after the defeat against Gouketsu).
- He tries to do the same with Saitama but, much to his horror, Saitama is unfazed from all his attacks and blows off half of his body, killing him.
- Driven by Envy: Admits he's always been jealous of Suiryu, which plays a big part in why he chooses to become a monster.
- Foil: To Suiryu and even more so, most heroes. While Suiryu seeks strength to have an easy life and most heroes seek strength to protect the innocent, Bakuzan wants to be strong only because he wants to torment everyone weaker than him.
- Jerk with a Heart of Jerk: After Suiryu asks him for his aid in fighting the monsters, Bakuzan looks like he's gonna consider it and commit to a Rivals Team Up...and then he refuses and chooses to eat a monster cell instead. Once his transformation completes, his first act is to brutally stomp Suiryu.
- Karmic Death: Subverted. Despite Suiryu asking him to help him fight the monsters after he realizes he can't do it alone, Bakuzan refuses and chooses to eat a bunch of monster cells so he can try and become the strongest monster, which seemingly overloads his body and kills him. Instead it turns out he survived and even became a Dragon-level threat in the process.
- Multi-Armed and Dangerous: His monster form has 2 pairs of arms which make his attacks deadlier.
- Sadist: In his monster form he loves torturing his victim physically and mentally. He brutalizes a heavy injured Suiryu by rapidly pummelling him as well as taunting him to the point of making Suiryu feel totally hopeless. His love for torment also goes as far as being willing to stomp Sneck in front of Suiryu in order to show that no heroes will come to save him.
- Unknown Rival: To Suiryu. He's envious of Suiryu and wants to beat him to prove he's the strongest, Suiryu gives him only a glance at best.
- When Saitama fights him as a monster, he keeps trying to remember where he met him before, forgetting he encountered him in the tournament.
Voiced by: Itaru Yamamoto (Japanese), Armen Taylor (English)
Sourface was once a disciple of Bang, but left after Garou rampaged through the dojo. Sometime afterwards, he created the Sourface Style Martial Arts and started his own dojo.
- Arrogant Kung-Fu Guy: Subverted, while he certainly thinks of himself as strong, he immediately understands how much weaker he is compared to the other contestants. Further subverted in his unseen fight with Jakumen; not only did he show complete sportsmanship, but he praised Jakumen's efforts after winning the match.
- The Bully: In the past was this to Charanko using him as a training dummy. However, getting beaten up by Garou seems to have mellowed him out and he's now sincerely worried about him when he saw his powerful opponents. Luckily, Charanko was actually Saitama in disguise.
- In a retconned chapter of the redraw, he actually attacked Charanko(Saitama)outside the match. However, this is no longer canon.
- Dumb Muscle: Not really a genius. For example, when Saitama loses his wig, Sourface is the only guy who doesn't understand that was a disguise and Saitama is not Charanko.
- Face of a Thug: As cartoonishly ugly as he is, he still has the appearance of a dangerous thug. However, he does show genuine concern for Charanko(Saitama in disguise)'s safety before he faces off against Choze, among other things. See Jerk with a Heart of Gold below.
- Gonk: His most noticeable feature is his taut face, strained to the point where it appears that he has been eating foods that were too sour, and a cleft chin.
- Jerk with a Heart of Gold: Originally bullied Charanko and still acted quite roughly to him in the present (actually Saitama disguised as him) but also showed surprising consideration such as helping him tie his belt properly, defending him when he was being trash talked by Zakos and showing concern at the opponents he would face. Also, in the one match he participated in, he showed great sportsmanship and praised his defeated opponent.
- Performance Anxiety: So much that he's completely paralyzed when the announcer introduces him. Of course, this is before he realizes just how strong the other contestants are.
- Younger Than They Look: He's barely twenty. That pinched, creased face makes him look like he's at LEAST in his late thirties. He's also rather sensitive about it.
Voiced by: Kentarou Tone (Japanese), Doug Erholtz (English)
A martial artist and user of the Fist Of The Pure Blood Master Race.
- A Nazi by Any Other Name: Seemingly invoked intentionally to draw him no sympathy. He wants his "superior" race to take over the world and he wants to prove that everyone else is worthless. He gets worse when he becomes a monster, deciding that all "inferior" beings must be wiped out and that he will eliminate anyone who doesn't pass his "selection process". He even has an attack that's designed to wipe out "inferior races". He is defeated by Saitama and killed by Suiryu.
- Arrogant Kung-Fu Guy: Choze is an arrogant man that looks down on others. He thinks that his masterpiece genetic material and the careful genetic breeding practices of his clan can make him and his clan superior to other normals and the feeble population of the Earth.
- Creepy Blue Eyes: Possesses these. They get even bigger and creepier as a monster.
- Curb-Stomp Battle: Defeats his opponents very easily, then gets defeated with one punch by Saitama, who finds him very annoying.
- Empowered Badass Normal: Easily kills Rosie, another participant who became a monster, and eats one of the monster cells to become a monster himself. He is able to have a close fight with Suiryu.
- Irony: By consuming a Monster Cell, he ruined the "perfect human" genes he was so proud of. This shows that he never really cared about being a "pure" human at all; he just cared about being better than others.
- Jerkass: During combat, he is quite vicious and bloodthirsty as he often beats his opponent to the verge of death. And he doesn't hesitate to eat a monster cell.
- Ki Attacks: After becoming a monster, Choze is able to use a technique that projects a powerful energy beam from his horns. It is strong enough to cause Suiryu to struggle while holding it back.
- Revenge: As a monster he vows to kill Saitama for humiliating him.
- Sadist: He is shown to be extremely sadistic, to the point where the screams and tears of his opponent are merely "fun" for him.
- Spikes of Villainy: In the monster-form, he grows spikes on his shoulders and his head seems to start to blend in with his attire. His hands become spiked and black.
- Super Breeding Program: He is extremely powerful because his clan chooses only the best genes to transmit.
- Super Strength: After transforming into a monster, his strength increased to the point where one punch is enough to send a contestant of the Super Fight tournament flying out of the stadium.
Voiced by: Koichi Soma (Japanese), Andrew Russell (English)
A martial artist and user of the Harsh Path Style. He and his dojo were the main antagonists of the Lobster special.
- Arrogant Kung-Fu Guy: Benpast is an arrogant man, looking down on heroes like Sneck.
- Butt-Monkey: He only shows up to get destroyed by everyone in one hit.
- Curb-Stomp Battle: Twice. From Sneck and, as a monster, Suiryu.
- Dirty Coward: He doesn't mind using tricks during fights, such as asking Sneck to stop only to strike him with an attack. He is also cowardly as shown when he runs away in an attempt to save his own life after Mysterious Beings attack the stadium.
- Power Up Letdown: When he becomes a monster, he gets a third eye and sharp teeth. That's it.
- Shout-Out: He is drawn in a comical style very closely resembling that of a pre-Z Dragon Ball villain. The third eye even resembles that of Tenshinhan from the same series.
- Third Eye: As monster, he gains an additional third eye.
- Underestimating Badassery: He assumes that Sneck is weak since he's the lowest ranking hero. Sneck is quick to correct that he is only the lowest ranking hero in A-class. He tries to punch Sneck, only to be counterattacked by Sneck's attack and defeated.
Voiced by: Yuya Murakami (Japanese), David W. Collins (English)
A martial artist and user of the Thunder Thunder Fist.
- Curb-Stomp Battle: He was defeated by Suiryu during the semi-final in 3 seconds with one single kick. Even after becoming a monster, he was no match for him.
- Lightning Can Do Anything: Volten was struck by lightning as a child, which turned him into a superb fighter.
- Shock and Awe: Volten is described as having a super conductor body. After becoming a monster, his electrical ability seems to have increased drastically.
Voiced by: Kaito Takeda (Japanese), Ethan Murray (English)
A martial artist and user of the Head First Rushing Style.
- Arrogant Kung-Fu Guy: He's both an allegedly major martial artist and also incredibly conceited towards his opposition, mocking "Charanko" at every opportunity as well as shooting jabs at Sourface. Turns out he's all bark and no bite, at least against Saitama.
- Butt-Monkey: Intended to propose to his girlfriend in his tournament victory while crushing "weak" martial artists. He not only ends up facing Saitama, his girlfriend never showed up in the first place, causing the stadium to laugh at his supposed weakness.
- Curb-Stomp Battle: In the tournament, he is quickly eliminated in one slap by Saitama disguised as Charanko.
- Long-Haired Pretty Boy: He is a young man with long, light colored hair that is slicked back.
Voiced by: Risa Tsumugi (Japanese), Lauren Landa (English)
Ring-Ring (or Lin-Lin, depending on the translatornote ) is a martial artist and user of the Palm Bell Fist.
- Anime Chinese Girl: Her look seems to invoke this trope. Resemblances to Chun-Li have been noted by several.
- Faux Action Girl: She is rumored to stand at the top of female martial artists. However, she was beaten by Max without any trouble (although Max disagreed) and was called a lightweight by Zakos. Comparatively, considering how overpowered some characters in One Punch Man are, she'd be an average martial artist of the lot.
- Punny Name: Her name in some translations, Ring Ring, is directly tied to the bells she wears and uses for combat.
- Ship Tease: With Max.
Voiced by: Arisa Sekine (Japanese), Lauren Landa (English)
A popular boy in Garou's past, who was also his childhood bully.
- Bishōnen: According to Garou, Tacchan looks like a pretty boy.
- The Bully: To Garou, as Tacchan always single him out into playing the role of a villain so he can defeat him as the hero.
- Dirty Coward: There is nothing to be considered brave or heroic by attacking social outcasts unprovoked. Both times where Tacchan fought against Garou, he tells his two friends to hold him down.
- The Faceless: He's only seen as a shadowy figure.
- Karma Houdini: He never gets punished for bullying Garou.
- Only Known by Their Nickname: He's only known as "Tacchan."
- Small Role, Big Impact: He was only seen Garou's flashbacks, but Tacchan's unfair bullying causes Garou to seek the path of becoming an all powerful monster in order to shake up the unfair status quo, of where those who are popular will always win while those who are hated will always lose along with instilling him the belief of an Ideal Hero.