Tormentor (noun)

A person who causes emotional or physical pain to another.

Origin:

From the latin word "tormentum" meaning "torture" or "pain" and the suffix "-or" meaning "one who does something".

Examples:

1. He was her tormentor and he made her life miserable.
2. The bully was the tormentor of the class.
3. The dictator was the tormentor of the people.
4. The abuser was the tormentor of his family.
5. The kidnapper was the tormentor of the hostages.