What does 'be a bad nut' mean?

The phrase "be a bad nut" typically refers to someone who is difficult, troublesome, or not trustworthy. It can imply that a person has negative qualities or engages in undesirable behavior, making them unreliable or problematic in social or personal contexts. The expression plays on the idea that just as a bad nut can spoil a batch, a person with such traits can disrupt a group or relationship.