Negative characters are attracted by their complexity and the need to somehow justify them in the eyes of the viewers and this is a real deep psychological work. There is no one hundred percent good and evil. Any hero, even Jack the Ripper, was born an innocent baby and was charming toddler as least until three years old. His journey from light to darkness actor need to build out of character. In the case of villains, there's always something to play. Take, for example, Raskolnikov's mental anguish. Pathological maniacs this applies less, though there's also room for imagination.
Psychologists believe that the role of the villains is attractive in that it makes it possible to realize (in virtual life) hidden desires, to open the dark side of your soul.
Very often bad heroes are much more charismatic than good ones. Some actors even gained such fame. For example, Anthony Hopkins is unmatched in the image of Hannibal Lecter, as well as his successor, who played a young doctor – actor Mads Mikkelsen. Gary Oldman rarely plays positive guys.
Christoph Waltz - charming gentleman, whose behavior is not a drop of aggression. However, this does not prevent him from playing a Nazi with an amazing hit in all the painful points of the viewer. From beneath the facade of friendly peeps out the smile of a sadist. Waltz plays brilliant villains so talented that even got the Oscar (the role of Nazi agent in «Inglorious Basterds» by Quentin Tarantino).
Christopher Lee played, seems, all the magical and fantastic villains, which only were in the movies. The audience doesn't even know if Saruman can smile. And for the role of the Joker Hollywood celebrities literally fought for life and death.
Women in this list are much smaller, but there are a few favorites. Actress Glenn Close is good in negative images due to her demonic appearance. Her Cruella De Vil is terribly scare not only dogs, but also kids. Helena Bonham Carter is incredibly organic in crazy Gothic outfits. Her Bellatrix Lestrange – a real brilliant of the Harry Potter’s movies. And finally about He-Who-Must-Not-Be-Named. Ralph Fiennes convincingly played not only Voldemort, but also the Red Dragon and even the SS in the "Schindler's List" movie.