One Punch Man: Which character could Saitama not one punch?

One Punch Man might come off as a superhero that a small kid imagines to be when they grow up, but the original series is much more than just punching monsters. The series consists of politics, power creeps, factions, friendships, and several other daily life aspects.

The protagonist himself appears to be an average everyday human. However, his power surpasses those that compare themselves to a god.

His name is Saitama, and as the title of the series might suggest, he can obliterate monsters and anyone in his path with just one punch. While his source of power is still in doubt, he is one of the strongest characters in the series, if not the strongest.

This power attracted an equal threat level as Saitama faced the first primary antagonist of the series, who he couldn't finish off with one punch. His name was Boros, who (like Saitama) also couldn't find thrill in battle because of how powerful he was.

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Boros was too durable to go down against Saitama's single punch in One Punch Man

The main antagonist of the Alien Conquerors arc, Boros, was Dark Matter Thieves' leader. He came to Earth not because he wanted to conquer the planet, as it was a matter too insignificant for him. Boros came after a prophecy told him that he would find someone "worthy" to fight there and that someone worthy later turned out to be Saitama himself.

After hearing Boros' backstory, Saitama gave his opponent the only thing he needed the most, and that was an all-out brawl. The reason behind Saitama not defeating Boros with a single punch might also lie in the former not facing a threat of Boros' caliber.

Saitama's standard punches to Boros (Image via One Punch Man)

Being so used to landing standard punches on his enemies and defeating them, Saitama started doing the same against Boros. However, Boros was, in fact, relatively more durable than any normal monster. Saitama also had to increase the strength of his punches amidst the fight, which led to Boros changing his form from normally armored to Meteorite Burst.

In Meteorite Burst form, Boros attacked Saitama with a series of punches, followed by an attack with his knee that launched the latter on the Moon. Saitama, being completely unfazed, jumps right back from the Moon to the Boros' alien ship on Earth, which both surprised and excited Boros.

Saitama's serious punch to deflect Boros' attack (Image via One Punch Man)

To counter Boros' next series of attacks, Saitama attacked with consecutive regular punches that tore the monster into pieces. However, he quickly reformed into shape due to his insane regeneration ability. After seeing Boros' attempt to end the planet, Saitama used his serious punch to repel the attack.

Saitama emerges victorious against Boros (Image via One Punch Man)

Critically injured, Boros laid on his ship, complementing Saitama for the battle he offered. Saitama also developed massive respect for Boros, as he was the first opponent he ever faced that his one punch didn't annihilate.