Klaus Voorhes was a lab assistant, bitten by an irradiated cobra he tried to use to kill his scientist boss in a way that looked as an accident. The irradiated cobra venom, combined with the anti-toxin he used to be safe of its bite, acted as a catalyst to give Voorhes cobra powers.
Cobra became a member of the Serpent Society and was generally loyal to Sidewinder, but when Viper took over the Society, Cobra sided with her out of fear. Viper sent Boomslang and Cobra under Copperhead's lead to poison the water supply of Washington DC, which they did despite Cobra's questioning of what kind of gain would they get from poisoning the city. While escaping through the street, the three villains found the citizens turned into snake-men similar to their teammate Slither, from which they deduced the "poison" actually was a mutagenic agent. When they reached their escape ship, they were intercepted by the Captain and Diamondback. The Captain defeated Boomslang and Copperhead, while Diamondback chastized Cobra for his betrayal, which caused him some remorse. He escaped and found Viper captured by Cap's other allies, so he tried to kill her but accidentally freed her due to Nomad's interference. After Viper made the Captain fight a mutated president of the USA, Cobra knocked her out and handed her to Cap in exchange for giving the Serpent Society 24 hours to escape. Rogers didn't accept, but Cobra gave him Viper anyways and ran away.
After Sidewinder retired, Cobra became the new leader of the Serpent Society under the name King Cobra.