That was dumb, just few chapters ago Emilia and Amelia were more powerful if not toe to toe with mc, yet so easily overpowered here.
Author could make Damned more logically stronger than trope perverted thugs, some kind of technological enhancements with ability to weaken anyone in contact, which would be reasonable for "Gestapo" like organisation.
Diedhauser most likely isn't a human, he is "on their side" but not "our side" while talking about humans.
Perhaps an android?
Speculation about girl from mc world being Fleonell sister got axed it seems, R.I.P. Lilenthal, you seemed to be a good person
Fleonell doesn't know how to get to his world either so far, so could probably cross that theory too unless she changed her appearance...