Mephisto

Golden Age Origin
Hawkins was a scientist obsessed with obtaining power. After years of research, he believed he had discovered a black magic formula that would make him "invincible." He claimed he would sell his soul for power and inhaled the gas produced by the potion. The gas instantly transformed him, causing him to grow devil-like horns. He then teamed up with Nazi fifth columnists, in an effort to spread chaos and terror, so that he could rule men with the scepter of fear. He was opposed by Doc Strange.

It is unclear what form Mephisto's "invincibility" took, once he was transformed. He was apparently strong enough to stun Doc Strange, and tough enough to take a hit from the super strong hero. It is clear that he was deadly accurate with throwing knives and capable of throwing more than one at a time with accuracy. He also used handguns and other weapons, and employed a small gang.

Golden Age Appearances
Thrilling Comics #30