The One-Punch Man manga/anime provides a constant flow of new monsters, each one giving its heroes the chance to showcase their strength. As the Hero Association and Monster Association battle each other we even see some humans evolve into the very monsters they fight in order to get stronger. So, what would happen if a human such as Suiryu -- who already possesses enough power to defeat most monsters as he is -- underwent this transformation?
Suiryu is a strong martial artist and a five-time champion of the Super Fight Tournament. His predecessor was also one of the best martial artists around while his grandfather, Suicho, created the Void First, one of the techniques Suiryo uses in battle. Although Suiryo seems to be something of a playboy off the battlefield, he's very perceptive with incredible brute strength when on it.
Just like Saitama, he wishes to fight stronger opponents since everyone in the martial arts tournament he enters is easily defeated by him. In fact, during the tournament's rounds, he intentionally prolongs the fight against one opponent just so he could enjoy it more before knocking them down with one kick.
Suiryu finally displayed his full fighting skills when he found worthy opponents: Saitama and the monsters; easily splitting the tournament stage in half while each of his footsteps was shown cracking the tournament floor as he walked over it. During his fight against Saitama, the metal bar around his arm broke when he flexed his biceps, further demonstrating his raw strength. Not only this, but he also has incredible speed and reflexes.
Suiryu was able to easily defeat the A-Class heroes who participated in the tournament. He displayed his endurance against Gouketsu and Bakuzan (Dragon-Level Monsters) defeating one of Gouketsu’s Three Crows with a single kick even after being injured. Despite being battered and bruised, he also still refused to join the Monster Association, proving that he's not only physically strong but mentally, too. But, what would happen if he did take the Association up on its offer?
After Gouketsu watched Suiryu defeat the newly turned monsters he offered Suiryu a chance to join the Monster Association, which the martial artist turned down. But if Suiryu had agreed, he would most likely be a greater threat than even Gouketsu. Prior to Suiryu’s fight at the tournament, he had initially engaged Garou in a virtual fight -- although they didn’t end the fight due to a system overload from the speed of attack from both sides. But Suiryu might have really stood a chance against the Hero Hunter in an actual fight considering his persistence against the two Dragon-Level monsters that almost killed him. And, like Garou, he would most likely break his limiter if he joined the Monster Association.
In the One-Punch Man series, Garou waged war on both the Hero and Monster Associations. But in the manga, each time he breaks his limiter he evolves into something more and more terrifying --something inhuman -- raising him to a Dragon-Level threat or more. His demonic-winged form actually proved too much for him, and he began to lose his power. To add insult to injury, he still lost to the One-Punch Man, too.
Suiryu is comparable to Garou since both are master martial artists who push themselves to fight stronger and stronger opponents. Considering how Garou broke his limiter in order to become more unstoppable, Suiryu could well do the same thing. And, with his greater mental resolve, he might have greater control over the new form this might unleash. Being able to achieve this level of monstrous power and maintaining it would make him nothing short of Saitama's greatest threat.