worrier

noun3

1. •
   A person who worries a great deal, especially unnecessarily.

   • You are such a worrier! I'm sure everything will turn out all right.
2. •
   An animal that seizes or shakes another by the throat.

   • The person owning a dog which had destroyed sheep could be made to pay for the damage; but the Court should also have an undoubted power to order incurable sheep-worriers to be destroyed. — 1886
3. •
   A person who causes worry in others.