Sadist (noun)

1. A person who derives pleasure from causing pain to others.
2. One characterized by sadism, the condition in which sexual or other gratification is linked to the infliction of physical or mental pain.

Origin:

From french sadiste, from the name of the marquis de sade, who wrote extensively on sexual violence and cruelty.

Examples:

1. He is a sadist, who likes to see others suffer.
2. He couldn't believe that she was a sadist, who enjoyed inflicting pain.
3. The sadist gets pleasure from causing pain to others.
4. He was labeled as a sadist because of his abusive behavior.
5. The sadist in him was pleased to see the other person in pain.