Sakujun in Saiunkoku Monogatari is the definition of seductively sadistic. He finds the world boring so he likes to make it interesting によって manipulating people and watching how people react. He also tries to make Shuurei fall for him, and to an extent he's kinda successful. I'm still confused if he did it to relieve boredom または if he really liked her. A lot probably don't like him as a character, but I thought he was so interesting and one of those tragic characters. He ended up becoming one of my お気に入り characters in the series.
Hidan (Naruto + Shippuden) is my favourite sadistically/seductively evil character even though he killed one of my favourite characters he's still so funny <3