Hannibal Lecter. One could easily believe that Anthony Hopkins was born for this role; in none other does he shine so bright and terrify so intensely.
Here, as an imprisoned cannibal, the only departure from the majority of sociopaths is his very high IQ (sociopaths tend to be of middling intelligence – they can appear intellectual but like everything else in their lives it is all an illusion).
Lecter is cold, calculating, deceitful, and emotionless. He derives a purely sadistic pleasure from his actions and even in helping the main character Clarice Starling (Jodie Foster) it is entirely for his own ultimately benefit. Nothing Hannibal Lecter does is for the benefit of others. Pure narcissistic sociopathy.