In the world of One Punch Man, the monsters that the heroes face keep getting stronger as the story progresses. One Punch Man starts with showing mostly those monsters that are on the lower levels, namely Wolf and Tiger, with Demon Level threats eventually becoming the norm. Stronger enemies can only be dealt with by stronger heroes and despite them going up against a Dragon Level threat before with Boros in One Punch Man season 1, episode 12, "The Strongest Hero", the strength of monsters keeps increasing.

Fast-forward to the Monster Association arc. In this arc, the S-Class and the rest of the Hero Association are pitted against an organization that works completely opposed to them. This organization is governed by monsters and contains threats from Wolf to Dragon Level, with the executives being known as the Monster Leaders. These are a collection of 9 of the most powerful Dragon Level threats that the whole Association has to offer with each being strong enough to destroy a city alone. So, let's take a look at who they are!

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Gums

Gums is a massive monster with a seemingly insatiable appetite. Gums can eat pretty much everything with its powerful jaws and its stomach contains a very powerful acid that helps it to digest whatever is in its stomach. It is an extremely powerful and durable monster that was shown to have eaten many other monsters before its battle with the S-Class, of whom he was able to defeat Rank 10, Pig God and Rank 15, Tanktop Master. Though both ultimately survived, Gums was able to do a great amount of damage to them but was killed by Fuhrer Ugly who ripped it open from the inside.

Nyan

Nyan was a Dragon Level threat with the unique ability to fit through any opening or crack and could grow his claws to viciously slash and maul his enemies. Nyan was extremely arrogant and confident in his rank as an executive cadre of the Monster Association as was seen when he still tried to go after Saitama right after witnessing Rover's defeat, however, he later ran away when he realized Saitama's strength. He was strong enough to defeat Puri-Puri Prisoner with little to no effort, but his arrogance got the better of him against S-Class hero Drive Knight, who was able to kill him.

Fuhrer Ugly

Fuhrer Ugly was originally a very ugly man who would never be taken seriously in society, building a lot of hatred and animosity within himself until it turned him into a monster. This hatred continued after his monsterization as he hated good-looking people the most and had a deep resentment of Amai Mask over everyone else because of this. His strength is one of the most formidable in the entire series as he was able to go up against many S-Class heroes and is extremely durable as he managed to fight off complete absorption by Gums' stomach acid, giving him his famous 'Vomited Fuhrer Ugly' form with acidic powers.

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On top of all of this, Fuhrer Ugly is incredibly violent and brutal, even more so than his fellow Leaders. This is seen when he brutally beats Tanktop Master, rips through Gums from the inside and tears Amai Mask into 2 pieces. He was finally defeated when Garou kicked a hole through his stomach.

Homeless Emperor

Homeless Emperor was once just an unemployed man who believed that humans were a stain on the Earth and nature. After being granted his powers, he went on to become a Monster Cadre and would use his spheres of light to wreak great destruction upon the Hero Association. Despite being the least durable of the Leaders on account of his fragile human form, he completely decimated Zombieman and kept many other S-Class heroes at bay with his Light Spheres. He was eventually taken by surprise and overwhelmed by Zombieman, leading to God taking away his powers and killing him.

Gouketsu

Of all the monster Leaders, Gouketsu is the one we know the least about. When he was a human, he was an incredibly skilled fighter as he was able to win the martial arts tournament and was then transformed into a monster. Though he didn't stay for long, he was still able to easily defeat S-Class hero Genos and then the martial artist Suiryu, who himself is stronger than many in the A-Class heroes. Finally, he also didn't pay any mind to the attacks by Bakuzan, whom he identified as a Dragon Level threat. Though exceptionally calm for a monster, he still met his end by Saitama punching his head off.

Elder Centipede

Elder Centipede is a Cadre that was shown before all others. What we know about his past is that he was powerful enough to fight against S-Class, Rank 1 hero Blast, though this was a battle that ended almost ended with Elder Centipede dying. His main goal in the series is to seek revenge against Blast, which leads him to fight Genos, Bang and Bomb together. However, this team-up of 3 S-Class heroes is still not enough to do much to Elder Centipede as his carapace is too tough and he just heals from the fire attack Genos does on his insides. The fight ends with Saitama killing Elder Centipede with a serious punch.

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Overgrown Rover

Despite being a member of the Monster Leaders, Rover acts more like a guard dog that protects the Monster Association headquarters. He is a giant, six-eyed dog monster and is shown to be even more durable than both Fuhrer Ugly and Gums in his fight with Garou, where he is dealt a massive and powerful strike by the Hero Hunter only to bounce back and end up defeating him. His durability is so great that he even ate a punch from Saitama, and on top of his durability, he is also very strong and can shoot powerful energy attacks from his mouth. His defeat by Saitama conditioned it to learn how to sit, eventually being adopted by Saitama at the end of the Monster Association arc.

Evil Natural Water

Evil Natural Water is a being that is considered by Psykos to be the most dangerous member of the entire Monster Association. The reason for this is that it is a mindless entity that cannot be reasoned with as it attacks anything that it senses hostility from, leading to it being locked away in a specialized container within the Association. Since it is just water, it can shapeshift almost unendingly to fit whatever shape it desires, as well as being able to shoot highly pressurized jets of water. After it got blasted away into the ocean by Garou, it was able to become one with it, growing astronomically in size and becoming Evil Natural Ocean, stronger than almost every other Cadre. But, Saitama defeated it with his serious punch, though very little of it survived and was swallowed by Pig God.

Black Sperm

According to most fans of the series, Black Sperm is the most powerful of all the Leaders. One of the reasons why this is the case is because of his sheer numbers during the Monster Association arc, where his cell count was at over 11 trillion individuals, each one of which was said to be strong enough to be in the A-Class. This allowed him to completely overtake the entire battlefield.

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Other than this, Black Sperm can merge most of their numbers to form an extremely powerful transformation known as Golden Sperm, which itself is a Dragon Level threat that can defeat almost every S-Class hero. This form easily overpowered Superalloy Darkshine and is perhaps the most durable of every cadre, withstanding powerful attacks from S-Class heroes as well as Fuhrer Ugly's acid.

However, if over 11 trillion of these cells manage to merge, they form Platinum Sperm, the strongest form of this character. This character not only has the strength of its Golden Form but has speed so immense that it is stated as one of the 4 fastest characters in the entire series. The three-way battle between him, Garou and Flashy Flash took place in a matter of seconds, where they were moving so fast that they made constellations in the sky. He and Garou eventually proved to be too fast for even Flashy Flash and they continued their battle, ending with Garou blowing up and killing Platinum Sperm.

One Punch Man is available to stream on Netflix and Hulu.

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