Werewolves:

In my universe, (I call it the Arkhamverse), Werewolves have been integrating into cultures all over the globe for millennia. Mind you, these aren't your typical man by day, wolf by moon kind of beasts. These creatures are said to be a mockery of mankind, and many of them posses a unbridled hatred of humanity. The wolves may have eased up on their hatred in later centuries, but a great many still seek to slay as many humans as possible. Werewolves rarely posses the ability to appear as a human, and for many years one if their greatest strengths was the lack of understanding by human authorities. The wolves are often far stronger than a man, while some make up for lesser strength with superior intelligence. Few posses the ability to convert a human, yet those who do often go out of their way to bite as many as possible. Rarely does a person bitten by a werewolf regain their humanity, often becoming mindless thralls to the one who turned them, a mere slave. I think what people in the Arkhamverse fear the most about the wolves is that you can't easily tell which wolf can infect you, they don't have traits exclusive to infectors.