Zombieman/Synopsis

History
Zombieman was created by Dr. Genus in the House of Evolution and was known as Subject 66. He was one success of the immortal series. 10 years ago, he managed to break free and got away, leaving behind a destroyed lab.

He once fought against a mysterious being in a fierce battle for 140 hours and emerged victorious. This event made him a bit famous.

Alien Conquerors Arc
Zombieman first appears in the S-Class Hero Association meeting, commenting on the lack of cooperation among the heroes. Later Sitch explains the matter of the meeting, stating the seer Shibabawa has died, which shocked Zombieman, questioning the cause of death.

Monster Association Arc
Zombieman arrives in W-City to track Marshall Gorilla, who left the field of battle to another side of the city to hunt other heroes. As he plans his course of action while trailing Marshall Gorilla, his plans hit a snag when the latter runs into one of the House of Evolution's test subjects, Armored Gorilla, who happens to be in the area and who beats up Marshall with a single punch. Due to the change in situation, Zombieman decides to trail Armored Gorilla to the House of Evolution's current hideout.

Upon finding the House of Evolution's current hideout through trailing Armored Gorilla, he decides to use his intent to eliminate them once and for all. Unfortunately, Armored Gorilla informs him that the old House of Evolution they once knew has already been defeated, much to Zombieman's surprise. While confronting Dr. Genus, while also having an axe prepared to kill the researcher with, Zombieman demands to know how the House of Evolution was defeated and why Dr. Genus has not rebuilt it. Genus tells Zombieman that he had witnessed a power more amazing than artificial evolution and that his research had lost. He explains to Zombieman the concept of "limiters" and that he had encountered a person, who we know is Saitama, who had succeeded in removing his. An unconvinced Zombieman sarcastically asks Genus if this person was strong enough to blow away Genus' whole ideology and had achieved such strength with no compensation, to which Genus tells him that the price this person had paid was that he became bald and suffered an overwhelming feeling of alienation. Zombieman is unamused by this, telling Genus he has lost it, and that he knows of many people that disregard their limits. Genus corrects him, explaining that these people were born with the possibility of becoming that powerful or had achieved it through mechanizing their body or human experimentation. However, this person, through effort alone, had broken past his natural limits, adding that he seems to be working as a hero now. A frustrated Zombieman asks why Genus started a Takoyaki shop. Genus tells him that he was researching cloning and had successfully created an unlimited amount of octopus tentacles.

Called upon by the Hero Association to raid the newly discovered Monster Association in Z-City, he immediately agrees to join because he was "in the mood for smashing that kind of organization."

Zombieman encounters Vampire (Pureblood). He is seen on the floor with an unfazed look despite his injuries. His bullets are useless against Vampire (Pureblood) as they are easily caught and released. Zombieman then tells his opponent to "prepare for some mud slinging" and 30 minutes later, he stands victorious in the middle of a bloody wrecked room with an axe slung over his shoulder. After taking about 200 fatal wounds from Vampire (Pureblood), he decides to rest, saying 3 minutes are needed for automatic full recovery.

Zombieman wanders around, wondering what the rumbling noise is about. Suddenly, Homeless Emperor is behind him who then blasts him with his energy spheres. He immediately gets up, much to his new opponent's surprise. He then asks how Homeless Emperor came to acquire such enormous power. It was a plan to stall time for his regeneration to work, but he comes to learn that a "God" had granted Homeless Emperor his "Divine Power". Unfortunately, Homeless Emperor had finished talking before Zombieman could fully recover and the two proceed to fight once again.

The next time Zombieman is seen, he has a huge hole in the middle of his body. He falls, and Homeless Emperor is seemingly the winner. But during the hero's all out fight with the association's Dragon-level monsters, he crashes out of the rubble and pins Homeless Emperor down. Homeless Emperor, who was apparently physically average had no means to free himself from Zombieman's grasp. The battle is won by Zombieman when God takes away Homeless Emperor's divine powers along with his life.

As the self-proclaimed "God Level Threat" Monster Garou defeats one hero after another, Zombieman steps up to stop him while knowing it is futile. As a result, he is reduced to a bloody pile in a matter of seconds. He recovers just in time to witness Saitama perform his Serious Table Flip.

Seeing Saitama has no intentions to kill Garou, Zombieman offers to kill Garou for him. However, Saitama and Bang refused to kill Garou because of having an empathy for Garou, understanding how he feels and what he truly wants; besides realizing he had saved a child whom the heroes thought to be kidnapped and about to be killed by Garou, thus letting him get away.

Psychic Sisters/Fall of Hero Associations Arc
By the time the Hero Association is about to fall soon enough, Zombieman returns to Genus informing him of what the former doctor said to him about how Saitama's power being reached through the removal of his limiter was true, and begged the doctor to make Zombieman's power equal to Saitama by having his limiter removed. However, Genus told Zombieman that in order for the hero to be on par with Saitama he'd have to do so under certain conditions after which he takes Zombieman to the basement of his Takoyaki shop.