piece of one's mind
Frank and severe criticism, censure, as in Chuck was furious and gave him a piece of his mind. The word piece here is used in the sense of “portion,” but the portion of the mind alluded to always has a negative opinion. [Second half of 1500s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.