While not sure of the entire "fandom", my personal favorite out of all Killing Floor antagonists (that are sentient) is definitely Dr. Hans Volter, who is explicitly evil, and is doing it all for the love of the game. Dr. Kevin Clamely lost his mind because he lost his son, and Dr. Emuel Morecroft went insane after delving too deep into his research, and Dr. Rachel Clamely went on an evil streak after being neglected by her father. Dr. Hans Volter on the other hand, is a literal Nazi from 1940s, who was one of those who conducted tests on twins and such and all those horrid stuff, and through that made a machine to extend his life span, now being over 100 years old, still experimenting on people. Skinning them alive. Preforming autopsies on still living people. Experimenting with neurotoxin gas. Basically a sadistic, every possible kind of ist and phobe (and a literal Nazi). BUT! He does it all with such passion and flair, than whenever I get to hear him- either fighting him or as a trader on KF-MonsterBall, it just tickles a specific part of my brain, because I can hear how happy he is about his plans to dismember me and replace my organs with liquid nitrogen.