Iwao Oguro (雄黒巌 Oguro Iwao?) is the vigilante known as Knuckleduster (ナックルダスター Nakkurudasutā?). He was formerly the Pro Hero known as High-Speed Hero: O'Clock ("超速ヒーロー" オクロック "Chōsoku Hīrō" Okurokku?) in Japan, and Hyper Quadfist (超頻四拳Chāopín sìquán?) in China.
Knuckleduster is a towering, heavily muscled man. He has short dark hair and visibly thick eyebrows, and also possesses heavy stubble and a prominent scar running diagonally down his left cheek.
His costume consists of a simple wrap-around mask tied over the top of his head, a tight-fitting dark shirt, jeans, boots, and a long trench coat. On his hands, he wears a pair of gloves topped with a pair of brass knuckles, or knuckledusters, from which he derives his name.
As O'Clock he wore a full-body suit and a case that covered his eyes and half of his face. He also wore gloves and boots, and his suit had several lines around the arms, legs, and torso. On his shoulders, he had what appeared to be his symbol.
Knuckleduster is an individual with a strong sense of justice and drives to do the right thing. He has no government-issued hero license, but this does not stop him from putting on his costume and going out every night to fight street-level criminals and local gangs to keep his neighborhood safe from crimes most "Heroes" will not bother with. Despite this reckless streak, he does genuinely admire Heroes for the work they do. This is probably because he also used to be a Pro Hero before his powers were stolen, which left him Quirkless.
Knuckleduster shows no resentment towards people who do and shows no fear towards villains who have powerful Quirks. In fact, he seems to love fighting against particularly strong people who have powerful Quirks, enjoying the challenge and becoming very upset or frustrated whenever there are no particularly strong Villains to fight. When a fight is too easy, he quickly becomes depressed. This seems to be one of the main joys of his life, as he becomes invigorated whenever he gets to fight a strong opponent. He is even willing to fight against Pro Heroes if the situation calls for it.
Knuckleduster seems to be a person with a tendency to use violence to solve any problem. He prefers to punch first and ask questions later, as he is willing to beat up people he deems to look suspicious on the slim chance that they may be villains or users of the Trigger drug, forcing his teammates to hold him back before he goes too far. His attitude extends that he was willing to attack a young-appearing woman under the suspicion of being a villain. Knuckleduster feels little to no guilt or worries about what he does, despite the fact that he could have been registered as a Villain if the misunderstanding continued, showing a more aloof and careless side to his personality.
However, despite this, he has proven to be more intelligent and perceptive than he seems to be at first. His conclusions are usually right, proving to have a great capacity for deduction. During fights he is able to devise strategies and stratagems very quickly to deal with villains with dangerous or problematic Quirk, knowing when is the best time to attack or what item is the most adequate to defeat them. And when he is not wearing his Vigilante attire, he can behave like a well-mannered and polite person, presented a perfect facade of a worker for a local non-profit organization, complete with business cards and a technically true spiel about the group.
The truth is, underneath his intimidating exterior and violent behavior, Knuckleduster is actually a very caring and good-hearted individual who cares for the people close to him and encourages them to achieve their goals. He trains Koichi Haimawari to improve his combat style and his Quirk and is proud of his progress. He is also a loving father and husband who holds a deep grudge against the people who hurt his family.
Overall Abilities: Knuckleduster is currently Quirkless, proven when Shota Aizawa tried to erase his Quirk to no avail. Despite this, however, Knuckleduster still possesses a large amount of physical strength and skill, which enabled him to fight on even terms even with a Pro Hero like Shota. Knuckleduster appears to be skilled in hand-to-hand combat, utilizing brass knuckles as his weapon of choice. Knuckleduster's skill with his fists was great enough to overcome the swordsmanship of Stendhal, a powerful and notorious Vigilante, landing a heavy blow before the vigilante could scratch him, and single-handedly defeating the swordsman.
- Enhanced Durability: Despite being Quirkless, Knuckleduster is very sturdy, standing up even when he receives blows from physical enhancement Quirks.
- Enhanced Strength: Knuckleduster's strength is surprisingly high, and he is sometimes mistaken for having a strength-enhancing Quirk. He was capable of going fist to fist with a tremendously physically powerful and fast moving Trigger-enhanced man and knock him out with relative ease.
Keen Intellect: Despite appearing to be a mere brawler, Knuckleduster has great intuition and tactical knowledge. When fighting Trigger-enhanced villains, he is able to work out how their Quirks work and the best way to counter them all while locked in a fight with them. He also quickly understood Stendhal's way of fighting as well as his state of mind, and also preemptively formulated a battle plan that would allow him to defeat Kuin Hachisuka whilst also saving the life of his daughter, Tamao.
Overclock (オーバークロック Ōbākurokku?): Iwao's Quirk allowed him to accelerate his brain's perception to extreme speeds, making it appear to him as if the world was moving in slow motion. While his Quirk was active, his accelerated perception granted him increased physical speed.
The Quirk requires a cool down period after it is used, and can only be used for a few seconds at a time.
- Heightened Focus: Thanks to his Quirk, O'Clock could see, hear, and think at hyper speed.
Brass Knuckles: Knuckleduster's main weapons and the reason for his Vigilante name.
Grappling Hook: Knuckleduster has been seen swinging from buildings by means of a grappling hook.
Pheromone Cocktail: An explosive cocktail made to draw in bees and then explode. Made with items obtained from Giran.
Sniper Rifle: A high-precision firearm, which allows shooting at a very long distance.
Radio Box: A regular radio box used against Number 6 to counter his usage of Overclock.
Shotgun: A firearm used for close range encounters.