Hellfire

Hellfire (ゴウカ, Gōka) is a monster and a member of the Monster Association.

Appearance
Hellfire has the appearance of a short robot with black and white armor and a cylindrical head.

Plot
Hellfire and his brother Gale meet Flashy Flash on route A in the Monster Association's headquarters. They both attack Flashy Flash, but are quickly decapitated by the hero, with both brothers asking each other what is going on as they have lost their visibility function.

Abilities and Powers
As a monster of the Monster Association, Hellfire is a fairly powerful being.

Immense Speed: Hellfire was apparently quite confident in his speed, but he was not fast enough to keep up with Flashy Flash who killed him with ease.

Trivia

 * Hellfire was a design from another mangaka back when ONE was still unemployed. That is the reason why they cannot be used in the redrawn version and instead replaced by Hellfire Flame.
 * It's unknown if Hellfire's existence is even canon to the webcomic anymore or if his existence has been retconned, as Hellfire Flame appears during the Ninjas Arc with no mention of Hellfire at all. It's also possible that the two are technically different beings in the webcomic.