Marvel Universe Appendix - Doctor Nemesis
I wanted to take time to explain this and since it centered around an Invaders story it is actually somewhat on topic. See Doctor Nemesis was originally published by Ace Magazines in the 40's which had no connection to Timely or any of it's later incarnations (ie Marvel). One day (1992-93) former Marvel EIC and Golden Age expert and fanboy Roy Thomas had an idea for a new Invaders miniseries which featured several of Timely's lesser known Golden Age heroes becoming feed up with not getting any respect and being lured in to work for the Axis Powers. But Mark Gruenwald, master of Marvel lore, nixed that idea and instead they decided to use characters from defunct publishers that had fallen into the public domain. Which is how we got the good doctor here in the X-Men and why he spends his free time killing Super-Nazi clones in Argentina.