Most One Punch Man fans are in agreement that Saitama is undefeatable since he spends the entire series searching for an adequate opponent. With the multitude of monsters and villains fighting against the Heroes Association, only a handful have proved challenging for the great Caped Baldy.
As the title suggests, Saitama generally only needs a single strike to defeat his enemies and, although he is always victorious (so far), some villains have piqued his interest. Fighting alongside the Hero Association, Saitama and his allies go up against Monsters and Ninjas to rid the world of evil. Japanese multi-millionaire Agoni started the Association to avenge his grandson's death, and Saitama joined for the «fun» of it.
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TheOne Punch Man heroes are evaluated within four tiers, C-Class, B-Class, A-Class, and S-Class, with the latter being the strongest. Do not be fooled by Saitama's low rank, which resulted from his work ethic and not from his skill level. Monsters, on the other hand, are grouped according to their threat level, starting at Wolf and increasing in severity through the Tiger, Demon, Dragon, and God levels. Ninjas are expected to graduate from the 37th Class of the Ninja Village, with the «Golden» title as the top status.
Spoilers ahead for One Punch Man
Speed-o'-Sound Sonic has made it his mission to defeat Saitama in battle. Regardless of how many failures he has racked up, the Ninja assassin keeps coming back for more. Although not officially ranked, Sonic's ninjutsu skills appear to be within the same level as an S-Class. He lives true to his name, as arguably the fastest fighter around, capable of giving Deep Sea King a run for his money. Additionally,
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