Defo Nazi Germany, though supposedly according to some tedious people I know, "they killed Catholics/Atheists too."
While the statement is true, they didn't kill anyone specifically for being Catholic or atheist. Also "Catholic/atheist" as a term makes no sense, since the two categories are mutually exclusive, "they killed Catholics and/or atheists too" is probably what you meant.
No, that's not what I meant. You can be a lapsed or cultural Catholic and a largely closet Atheist at the same time, as I can attest. So potentially two (unlikely) reasons to die.
But I'm dirty blonde/blue-eyed, so I'd probably be okay, and the USSR sounds like even more of a hellscape.
ETA: After second thought, on moral grounds if you have a choice I think you have to go with 30s USSR even though its way less pleasant an existence.