Ribby

Where most Nomu run bulky, Ribby is gaunt: his frame looks shriveled and underweight, carrying little muscle by High-End standards. His bones show through, and the ribs jut outward from inside his chest, which is where the name comes from.

The build is otherwise humanoid, as with nearly all Nomu, topped by a long antenna-like head that can stretch well past its resting length.

He was built out of a killer's corpse and it shows. The moment he wakes, he wants heroes dead, and he goes after that with no restraint whatsoever.

Some intelligence survives the conversion, though. He recognizes and understands what is around him and who he is fighting, and he turns what he notices to his advantage.

Before Garaki got to him, Ribby was a psychotic serial murderer, and the doctor picked him for conversion into a High-End precisely for that reason.

When the heroes launch their raid on Jaku Hospital, Garaki moves to warp himself clear along with Tomura Shigaraki, using Johnny's power, but Mirko crashes into the lab and kills Johnny in the process. Cornered, the doctor releases five High-Ends, Ribby among them, to buy himself time with Tomura. Under Woman's improvised command they attack, and because none of them got their stabilization period, Mirko drives them back easily.

The fight turns as stabilization catches up and the Nomu grow comfortable inside their bodies. Mirko breaks off to reach Garaki and Tomura; Ribby shoots his antenna out after her and hauls her back before she can wreck the capsule. Endeavor drops onto his head out of nowhere, freeing her to smash it open. Eraser Head arrives and erases several High-Ends, Ribby included, to make them killable, but Woman works out the trick and buys Ribby the seconds he needs to strike again, running his antenna through Mirko's chest and legs, taking an ear, and dragging her away before Endeavor pulls her out. He keeps fighting until Tomura, newly awakened, brings the hospital and lab down with Decay, wiping out much of the raid team along with every other High-End. In one last gambit Ribby seizes the fleeing Eraser Head and threatens to spread the Decay into him; Crust cuts the arm away with his Shield, dying alongside him.

He carries three powers. Super Regeneration, standard for every High-End, heals whatever damage he takes. An unnamed antennae Quirk extends the growth on his head to significant length, letting him seize or impale objects and opponents outright. An unnamed rib cage Quirk reshapes his ribs for a range of purposes, attacking and defending among them. Even injured and stripped of all three by Erasure, raw strength let him crush Eraser Head's leg without effort, and his speed matched Mirko's movements closely enough to intercept her and to block an unexpected Jet Burn thrown by Endeavor.