Hammerhead is a tall muscular man with a horizontal scar across his nose. Like the rest of Paradisers, his head is bald and he wears a black, full-body battle suit, although his rank is indicated by unique flame decals emblazoned across its torso and thighs.
As head of the Paradisers, Hammerhead strives to create a utopia in which work is voluntary, and the unemployed receive full financial support. Despite his leadership role, he lacks the charisma to rally any support for their misguided cause and resorts to terrorism to garner attention.
After several futile appeals for a revolution towards passerbys in F-City, Hammerhead leads his Paradisers, outfitted in stolen high-tech battle suits, on a mission to demolish the mansion of Zeniru, which he views as a symbol of social inequality.  After they destroy the wrong building, they easily defeat the riot police and Mumen Rider, but are intercepted by Zeniru's bodyguard, Speed-o'-Sound Sonic, in the woods around Zeniru's mansion.
Hammerhead rejects Sonic's call for surrender and attacks him, only to see his entire Paradise Group massacred, and narrowly avoids death himself. Despite leveraging his suit's immense strength against Sonic and using clever strategy, he is stabbed in the back of his head with a kunai and presumed dead. 
Thanks to his thick skull, he survives and flees the scene, only to encounter Saitama, incensed at being typecast as a member of the Paradise Group. After receiving a blow to the face from Hammerhead's suit, Saitama expresses disappointment at its pitiful strength, prompting Hammerhead to trigger the battle suit's full power. Saitama remains unimpressed, but feels a trace of empathy for Hammerhead, and merely destroys his suit rather than kill him.
Hammerhead is left naked and allowed to escape, but is found, beaten, and left for dead by robotic assassins from a mysterious group known as The Organization, surviving again due to his thick cranium. Lying in his own blood, he cries streams of tears, thanking his mother for giving him his thick skull. He then vows to give up his cause and look for a job.
During an investigative briefing at the Hero Association HQ, A-Class Superhero Sneck reports sightings of Hammerhead outside of a job center in F-City, wearing a formal suit and nervously preparing for a business interview.
He and some of the prisoners are trained by Puri-Puri Prisoner to fight monsters and it is shown that his strength has improved to the point that he can fight Wolf-level monsters without his battle suit.
When Raiden and his Neo-heroes try to turn them into cyborgs, he and the rest of his group prepare to fight the Neo Heroes.
Abilities and Powers
As a B-Class criminal, it can be assumed that Hammerhead is a reasonable threat, being able to match B-Class heroes in terms of power.
Enhanced Strength: Even without his battle suit, Hammerhead possesses a great amount of physical strength, being able to hospitalize twenty people.
Thick Skull (超頭骸骨, Chō atama gaikotsu): As his name suggests, Hammerhead possesses a cranium several times thicker than a normal human's and dense enough to withstand bladed and blunt trauma. On multiple occasions, this has allowed him to survive injuries that would normally kill a person.
Enhanced Senses: Hammerhead appears to have above-average level senses. This is seen when he was able to sense something wrong while on his way to Zeniru's place, which was Sonic hiding in the shadows.
Proficient Hand-to-Hand Combatant: Hammerhead has a history of street brawling, having once put twenty people in the hospital. Despite his plain appearance, he employs some amount of strategy in combat, using his environment to set up crude choke points for his opponent.
- Spin Attack (グルグルアタック, Guruguru Atakku): Hammerhead rapidly swings his arms back and forth.
Battle Suit (Formerly) : Hammerhead's battle suit protects him from all manner of attack and enhances his strength to superhuman levels, enough to create ground-splitting shock waves and lift massive objects with ease. The suit was destroyed by a single hit from Saitama.
- Full Power (フルパワー, Furupawā): Under duress, Hammerhead can further augment the suit's power to gain even more size and strength, though its extent is not shown.
|Hammerhead and Paradise Group vs. Speed-o'-Sound Sonic||12, 13||4||Loss|
|Hammerhead vs. Saitama||14||4||Loss|
- In the 2017 One Punch Man Halloween cover, Hammerhead was depicted as the spirit of legendary Japanese warrior monk Benkei, famous for dying on his feet after being struck by multiple arrows. In Hammerhead's case, he still has Sonic's kunai stuck on the back of his head. Hammerhead is ironically the complete opposite of Benkei, as he fell dead against Sonic but survived.
|S-Class||Gale Wind • Hellfire Flame • Speed-o'-Sound Sonic|
|A-Class||Bull-Bull • Serial Bomber|
|C-Class||Banero • Don Pacino • Pacino Family|
|Ex-Villains||Dr. Genus • Hammerhead • Men's Esthetician Man|
|Undetermined Class||Aburabozu • Base B • Burigura • Chimagusa • Coalition of Assassins • Cow's Stomach • Demolition John • Devil Storm • Fukegao • Garou • Harold • Paradise Group • Smelly Lid Old Man • Special Moves Mile|