A person who thrives only on the unhappiness of others is often referred to as a "sadist." Sadism is a psychological trait where an individual derives pleasure or satisfaction from causing physical or emotional pain, suffering, or humiliation to others. It is considered a form of cruelty and is not a healthy or acceptable behavior in social contexts. Sadism is often associated with personality disorders or other underlying psychological issues. It is important to recognize and address such behavior, as it can be harmful to others and the individual exhibiting such tendencies may need professional help or intervention.