Lots of things could point to low self-esteem.
Such as:
An afflicted Sun, such as Sun opposite Neptune, or Sun square Saturn..Both could indicate a lack of feeling good about the self, whether through the inability to see the self clearly, or by feeling overlimited..
An afflicted Moon, an afflicted Moon in my experience always indicate some level of insecurity, it doesn't even have to be afflicted.Even an overly strong Moon can indicate insecurity. Moon conjunct Mars in Cancer in ninth house conjunct MC is the neediest, most dependent guy I know..Might be exaggerating... Moon in Pisces also sem insecure and overly emotional to me, but I think it's just a subjective thing..
Any affliction with Saturn could indicate a low self-esteem, because there may be a feeling of limitation and an unableness to get things just right. Like a Moon - Saturn affliction could feel unloved in the home, which creates insecurity elsewhere, or a Venus - Saturn affliction could feel unworthy in their relationships..