DC revealed that Superman’s alien DNA is a dark way for villains to get an upgrade. Superman’s genetic structure is what gives him all of his fantastic powers, and in 1987’s Action Comics #590, the villain Chemo benefited from it as well, gaining a massive power upgrade, making him a true threat to not only Superman, but the entire world.
As a native of the planet Krypton, Superman’s DNA is markedly different from humans. While different generations of writers have reinterpreted how Superman derives his powers, his Kryptonian genetic structure remains at the core. Thanks to his alien heritage, Superman can absorb the sun's solar radiation, charging up his cells, which gives him super-strength as well as the ability to fly. In 1986, writer/artist John Byrne revamped Superman for the modern era, radically depowering the Man of Steel and focusing more on his humanity. Byrne changed how Superman’s powers developed - in previous iterations, Superman’s powers developed as soon as he arrived on Earth and bathed in the light of the yellow sun, but Byrne changed this, revealing that Superman’s powers developed gradually as he aged. This was not the only change to Superman that Byrne made, and in Action Comics #590, readers learn that Superman’s DNA can also give villains, such as Chemo, serious upgrades.
In the issue, written and drawn by John Byrne, Lois Lane and Clark Kent are touring a chemical factory, where, unbeknownst to them, one of the vats contains the remains of Chemo, who had been seemingly killed during the Crisis on Infinite Earths. During their investigation, Clark accidentally stumbles and falls into the vat containing Chemo’s remains. He is unharmed, and after being rescued, he and Lois continue onward. Later, the vat containing what is left of Chemo comes to life, taking Superman’s shape and embarking on a destructive rampage, ultimately taking the combined might of Superman and the Metal Men to take him down. Later, Superman learns that when he fell into the vat, bits of his DNA mingled with Chemo’s remains, which not only restored him to life but upgraded his power levels as well.
There Is Massive Potential for Evil in Superman's DNA
Superman’s DNA makes him one of the strongest beings on Earth, and as such it has proved tantalizing to geneticists and super villains alike, but ironically one of the first to benefit from it was an unwilling participant. Superman’s DNA gave the vat of chemicals that was once Chemo a jolt, bringing him back to life as if he was Frankenstein’s monster. This alone is a fantastic feat in itself, but to also give Chemo so powerful an upgrade he nearly took Superman down to the wire shows just how unique Superman’s DNA really is.
Thankfully, Superman guards his genetically material relatively well, though he has been cloned in the past - most notabkly by Lex Luthor, who created a freakish Bizarro clone, and Cadmus, who created Connor Kent's Superboy from both Superman and Luthor’s DNA. However, Chemo showed that even a direct transfusion of Clark Kent's Kryptonian DNA can elevate a villain to god-tier powers, showing the immense potential for evil Superman's genetics have when the wrong people get ahold of them.