Deep Sea King

In his dehydrated state the Deep Sea King looks the most human of the Seafolk, a hulking, muscular figure whose arms, legs, and back are dark green while his chest and stomach stay pale. Fins jut from both sides of his head, small pink ovals sit where eyebrows would be, and a wide, fanged mouth rests beneath sharp eyes. He dresses in a red speedo, an elaborate crown, and a fur-lined cape clasped at the front with a fish-head fastener, and his chest sports heart-shaped nipples.

Given enough water, he swells into a far more menacing shape. A dorsal fin runs the length of his spine, new fins erupt along his forearms and shoulders, and the ones on his head lengthen. His coloring shifts to aquamarine as his features shed their human cast and grow bulkier and more beastly.

Cruel and combative, the Deep Sea King relished picking fights and inflicting pain. He meant to seize the surface world for his own rule and regarded humans as nothing more than prey, feeling no guilt about treating them that way. His arrogance ran deep: he saw himself as a superior being perched at the summit of a pyramid encompassing every living thing on the planet.

The Deep Sea King rises out of the water in J-City after Stinger clears out his underlings, felling the A-Class hero with a single strike. He batters Lightning Max next, whose blows barely register, then faces the S-Class Puri-Puri Prisoner, who has broken out of Smelly Lid Prison alongside Speed-o'-Sound Sonic. At both partial and full power, Puri-Puri Prisoner is beaten down and hurled through a building. Sonic fares better, slipping past the monster's punches and severing the eel that lunges from its mouth, but once the rain restores the king to his true form he can barely keep his distance and flees, leaving only his shredded clothes behind.

Drawn by a mass of life signs, the king breaks into J-City's evacuation shelter. He crushes the heroes who step up to stall him, among them Jet Nice Guy, Bunbun Man, Sneck, and All Back-Man, before an enraged Genos blasts him out of the building. The two trade heavy blows; the king tears off one of Genos's arms and spits acid at a fleeing child, which Genos takes on his own body to shield her. Beaten and bloodied, Genos is saved when Mumen Rider throws himself into the fight despite hopeless odds. The king swats the C-Class hero aside and knocks him straight into the arms of the newly arrived Saitama. A single casual punch from Saitama tears a hole clean through the king's body, unleashing a shockwave that halts the rain and ends his life.

The Deep Sea King ranked among the stronger Mysterious Beings, able to defeat several low-ranked S-Class heroes. His fish-like biology let him breathe both underwater and on land, though without moisture he weakened into a shriveled, dried-out state; soaked in rain or seawater he changed into a bigger, faster, and far deadlier natural form. He wielded immense strength and durability, shrugging off attacks from A-Class heroes and cracking buildings apart, while a rapid healing factor mended wounds mid-fight, albeit not fast enough to survive a lethal enough blow. He could fire acidic spit that dissolved even Genos's metal frame, launch a body moray from his throat, and sense presences all around him, and in combat he favored relentless flurries of punches, including a battering technique called Barrage.

His death left a lasting mark. Losing to him spurred both Puri-Puri Prisoner and Lightning Max to grow stronger, while the trauma pushed All Back-Man to quit heroics altogether. Later Seafolk, including the self-proclaimed second Sea King Lord Great White, sought to avenge him, and the creators have named him among their favorite monsters for the impact he made on the series.