The joker was all emotional indifference and cowardice behind the layered mask of white.
The joker was entitled and vain, prising his own emotions and treating others as if they were nothing at all. For this is real evil, indifferent to others and yet feeling angry when the world does not appear to revolve around them as the underdeveloped brain believes it must. The villain, despite apparent intelligence, is the owner of a brain as disfigured as the face of the joker.
The joker minus the makeup was the most impetuous bore, between his addictions and tantrums his henchmen were little more than his manifestation of daddy-issues.
The joker is all ego and no empathy, as cold within as it is possible for a person to become, addicted only to the sickest substitutions for emotional connection. Instead of loving people he hurts them. Instead of friends he makes enemies to destroy. Instead of a loving family to protect and be protected by... he has paid thugs. The sad truth is, this is how villains make relationships, because it's all they can achieve, it's all they have.