Fukegao

Gaunt and pale, Fukegao carries a heavily lined face framed by thin black hair split down the center and hanging past his long jaw. His wardrobe is the standard uniform of his trade, a black shirt worn under a full-length white lab coat.

Power-hungry and grandiose, Fukegao dreams of ruling the world and brands himself the single smartest person alive, a boast his invention lends some weight to. He is arrogant, cruel, and detached from reality, barking at his brother during their rampage to level more towns and pile up more corpses as proof of the steroid's might. Beneath the megalomania sits genuine affection for Marugori, however. The formula seems built expressly for his sibling's wish to gain the ultimate body, and in the anime he mentions adding strawberry flavor so it would go down easier. He longs for the two of them to reign together, wary of the drug's raw power yet never once tempted to drink it himself.

After long labor Fukegao completes his masterwork and hands the vial to Marugori, whose body erupts to the height of a skyscraper once he drinks. Crowing that they, the Brain and Brawn Brothers, are destined to seize the world, the scientist is briefly pinned beneath his collapsing laboratory before his brother digs him out and perches him on one massive shoulder. From there he eggs Marugori on as the giant flattens D-City block by block, reveling in the destruction and urging him toward the next town.

The celebration turns fatal at B-City. Spotting Saitama balanced on the other shoulder, Fukegao shrieks for his brother to swat the intruder, but Marugori clubs the wrong side and inadvertently crushes his own sibling. Possessed of no powers beyond a brilliant mind, Fukegao leaves behind only the Dragon-level menace he created, and he holds the grim distinction of being the first named human death in the series.