blunt instrument

noun2

1. •
   An object lacking sharp surfaces, especially as used to cause injury.

   • One deep wound had been inflicted upon the temple, apparently with some blunt instrument, which had penetrated the brain. — 1851
2. •
   (figurative) A thing, person, method, or resource which is not sufficiently precise or not sufficiently effective for its intended role or use.

   • The analyst is in a sense a blunt instrument, but he can work as somebody who cares, and I think a good analyst makes the patient feel that he has value. — 1987