It can mean multiple things.
One, a deep sense of insecurity & inferiority. Feeling as if they are less than you, so are not good enough. Basically, a self esteem issue.
Second, they have crossed moral lines. They could be a “bad person” who has done “bad” things. So, they are not good enough because they are bad for doing bad things.
There could be other things surrounding that, but mainly
Low esteem &/or they have committed corrupt actions.
