Doctor Nemesis was an ordinary physician named James Bradley with an extraordinary gift for fashioning drugs, such as his own truth serum. When his daily work led him to crimes, he donned his surgical mask to fight for justice!
Doctor Death was an ordinary physician named James Bradley with an extraordinary gift in multiple scientific disciplines. When his daily work led him to crimes, he would don his surgical mask to fight for justice - until the Nazis made him a better offer!
The Story Behind the Story: Doctor Nemesis fought criminals and Axis threats in a brief, undistinguished run of stories at Ace in the 1940s. He might have remained in the musty history of comics but for Roy Thomas, who wanted his 1993 Invaders mini-series to feature Golden Age heroes who switched sides to the Nazis. Mark Gruenwald objected to this idea, so instead of using Golden Age Marvel heroes, Thomas employed non-Marvel characters, such as Doctor Nemesis - renamed Doctor Death. In fact, Doctor Death was the principal leader of the book's Battle-Axis; he also turned out to be the creator of the android Volton (somewhat outside the providence of a medical practitioner) and ended the limited series quite dead, electrocuted by an upset Volton.
More than a decade later, something quite curious happened; X-Men scribe Matt Fraction got hold of the character and brought him into his book's cast, taking advantage of his previous Marvel appearance but otherwise completely ignoring it; he was alive, again called himself Doctor Nemesis and was staunchly anti-Axis (to the point where his anti-Nazi rhetoric was practically a running gag). The only thing Fraction kept from the Invaders appearance was the idea that Doctor Nemesis was a practitioner of comic book science - meaning, he could do anything (and thus repeat various tired "science!" internet memes). Doctor Nemesis has, surprisingly, become a useful member of the X-Men cast, with his misanthropic ravings proving quite popular. His time spent living and dying as a Nazi collaborator have been forgotten. Depending on how you regard these circumstances, he's been either two different characters or three!
Come back tomorrow for the final "Curiously Familiar."