From Pluralpedia, the collaborative plurality dictionary
sadist (n.)

A sadist is the opposite of a Masochist, they are sadistic in nature as part of their role. They can be sadistic towards those outside of the system or those within it. This could be its own role, or part of a larger role. They might be sadistic as a means of protection, and making what they protect from less stressful or more enjoyable for them. They might be sadistic towards other alters as a means of persecution, as part of their role as a sexual alter, or something else.