What is an underdeveloped personality?

An underdeveloped personality is a person who has not learned how to fully and properly behave, think, feel, interact socially, control self, express self and to feel remorse for bad behavior. Think of a baby. The baby has not learned to be an adult and to be a fully rounded person yet. If someone fails to thrive and "grow up" properly or is traumatized there can be personality malfunctions.