Sadistic means taking pleasure in the pain of others. A sadistic streak, sadistic cruelty, sadistic pleasure.
It is a serious charge and a clinical term both, and using it lightly — a sadistic exam paper — is common and slightly awkward. It is named after the Marquis de Sade, whose novels described exactly this. Note sadism; and that masochism is named after Sacher-Masoch in the same way, by the same psychiatrist, in the same book.
1adjectivesadisticTaking pleasure in the pain of others.
“The sadistic guard smiled as he took away the prisoners' food and blankets.”
sadistic is a quality of cruelty.
From sadist + -ic.
Etymology from Wiktionary, CC BY-SA