bad sort, a - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An unpleasant, mean person, as in We cautioned Bill about his friend, who was clearly a bad sort. The antonym is a good sort, a pleasant, kind person, as in She's a good sort, always helping her neighbors. The latter is stronger than not a bad sort, as in He seems ill-tempered now and then, but he's not a bad sort. All three terms use a sort in the sense of “kind of person.” [Second half of 1800s]