spite
A mean desire to hurt or upset someone on purpose.
Spite is the desire to hurt, annoy, or upset someone because you're angry at them or want revenge. When you act out of spite, you do something specifically because you know it will bother someone else, even if it doesn't really benefit you.
If your sister refuses to share her art supplies with you, and you respond by hiding her favorite pencil just to upset her, that's spite. If two classmates stop being friends and one tears up the other's drawing out of spite, they're acting from a mean, petty desire to cause hurt. Sometimes spite makes people do things that actually harm themselves, just to get back at someone: imagine refusing to go on a fun field trip only because someone you're mad at will be there.
The word can also appear in the phrase in spite of, which means “despite” or “regardless of.” If you succeed in spite of many obstacles, you succeed even though those obstacles tried to stop you.
Acting spitefully usually makes situations worse rather than better, and the spiteful person often ends up feeling worse too. Spite is what happens when anger turns petty and small, focused more on hurting someone else than on solving the actual problem.