Something that's violent involves physical force or emotional intensity. If you hate violent movies, it means that you don't want to watch scenes of people being hurt or killed.
Physically violent behavior ends in someone getting hurt or something being destroyed or damaged. You can also have violent emotions, like a violent burst of anger toward the slow driver in front of you, and you can use violent to describe something that's visually intense, like a violent orange-colored minivan. The word has gained in force since developing from the Latin word violentia, which means "vehemence or impetuosity."