WARNING: The following article contains spoilers for One-Punch Man Chapter 106 by ONE and Yusuke Murata, available now in English from Viz Media.
One-Punch Man Chapter 105 saw Terrible Tornado take down Gyoro Gyoro, the Monster Association's strategist. As he lay defeated, the villain called for backup from Lord Orochi, the Monster Association's boss and strongest warrior. However, Orochi wasn't able to assist Gyoro Gyoro, as he was already occupied with Saitama. Chapter 106 encompasses the whole battle between the two, and the victor isn't in the least surprising.
The hero easily dodges Orochi's opening flurry of attacks, which involve him using his snake-headed limbs against Saitama (In Japanese, "Orochi" means "big snake," and the villain is something of a reference to Yamata no Orochi, a multiheaded monster from Japanese legend). It's then revealed that Pochi, who Saitama punched in Chapter 104, is still alive. However, on being ordered to attack Saitama, Pochi flees, shocking Orochi. Saitama reveals that he held back against Pochi, because he's a dog. As Orochi is a monster, the hero doesn't plan on being as nice to him.
Orochi then realizes that Saitama is "the threat that was incomprehensible," and identifies him as the one who previously killed Goketsu and Centichoro. Orochi gets quite excited for the fight and powers up, declaring this to be "the ultimate battle," with Saitama as the pinnacle of human strength and Orochi the "supreme lifeform." Before Orochi can go into his long introduction -- as is typical for One-Punch Man -- Saitama stops him, saying he'll defeat the monster in a single punch and that he's not expecting much of a challenge.
This enrages Orochi, causing him to attack Saitama. The hero easily bats away Orochi's snake limbs and massive energy blasts, which nearly blows away heroes nowhere near the action while also devastating the city above. In response, Saitama dashes at Orochi and, after a short kerfuffle, punches right through the monster. As Orochi's body falls into the abyss over which they've been fighting, Orochi feels fear and is defeated.
Orochi has generally been assumed to be the Monster Association's most powerful villain, and he fell to Saitama without much trouble at all, further establishing just what a dominant force the manga's titular One-Punch Man is in his universe. At this point, it seems unlikely anything could really rise up to challenge him, but Shibabawa's prophecy and the destruction of Earth could finally determine if there's anything that can stand in the hero's way.
One-Punch Man's next installment arrives in English on November 13 from Viz Media.