Metalo of Earth-2
The powerful parallel world armored scientist who is the sworn enemy of the Superman of Earth-2. Metalo is the criminal alias of mustachioed George Grant. The chronicles are unclear as to whether Superman's earliest encounters with Metalo occur on Earth-1 or Earth-2 [see Metalo of Earth-1].
In April 1982, the Superman of Earth-2 is secretly hit with a ray beam by Metalo. Less than 24-hours later, Superman and Lois Kent are surprised to discover that Superman's powers have been decreased considerably, to the point where "leaping only an eight of a mile," "hurdling a 20-story building," and running "about 70 miles an hour" is the best he can do. Outmatched in terms of strength by Metalo, Superman must rely on his unaffected heat-vision to temporarily fend off his enemy.
Reduced to driving a car to his mountain retreat [see The Secret Citadel], Superman engages Lois as a personal trainer to help rebuild his strength with the aid of "the world's most amazing gymnasium." Noting that, "it took years to build my physique to what it is today," Superman nevertheless embarks on a "crash-program" of weight-lifting, running, gymnastics, and finally flying, until he looks "more powerful than ever." Handily defeating Metalo in a rematch, the reinvigorated Man of Tomorrow is pressed into service ghost-writing his wife's report on the Metalo encounter, Lois being exhausted "after two days of training" Superman back into shape (SF No. 217/1: "Back to Square One!").