maniac

/ˈmeɪniæk/
noun
  1. A person who behaves in a wild, violent, or extremely enthusiastic way.
    • The movie villain was portrayed as a dangerous maniac with no remorse.
    • The driver was a maniac, weaving through traffic at high speed.
    • He's a maniac when it comes to video games, playing for twelve hours straight.
adjective
  1. Wildly enthusiastic or obsessed with something.
    • The maniac crowd cheered nonstop throughout the entire game.
    • She's a maniac fan of that band and has seen them in concert twenty times.
    • My brother is maniac about keeping his car spotless.