Other forms: sadistically
If you kick your little brother in the shin and feel a strange sense of enjoyment as you watch him cry, then you’re being sadistic, meaning that you get pleasure from hurting others.
The Marquis de Sade was an 18th century French nobleman who became known for his unusual practices — which included finding pleasure from causing others pain. From the Marquis, we get the word sadism, which is used to describe someone who gets a strange enjoyment out of making others suffer. Someone who is sadistic might feel a cruel thrill from kicking a helpless puppy or making a child cry.