The use of a character's interest in BDSM or similar to reinforce the idea that they're evil, probably because of the Cold-Blooded Torture symbolism. Portraying them as creepy and hideously unsexy can also ramp up the "ick" factor. If played straight, it's often reinforced with hints of Putting on the Reich or whatever. A woman who's Dressed Like a Dominatrix will often be portrayed as a villain in fiction — or at least a violent type — for this reason. Note that this is rapidly becoming a Discredited Trope — with the rising mainstream acceptance of alternative sexualities, using this trope straight will often raise the ire of many real life practitioners. Compare Too Kinky to Torture , where someone is so tough that torture gets them off, and Combat Sadomasochist.