The "Steel Devil" is the fan name for the unidentified giant Devil-like robot that Dr. Wily uses in the climax of the Mega Man comic book series by Dreamwave Productions. The exact size is a bit uncertain, but comparison between it and the tiny Mega Man and Proto Man at its feet (they're the red and blue dots in that yellow circle of astonishment to the right) suggests that it may be bigger than Gamma by a fair amount.