Originally the term sociopath was used to describe someone with no shame or guilt, whereas the term psychopath was used to describe someone with no remorse or conscience. However, in recent times both terms have started to become used interchangably, though they are now considered to be derogatory.
Both sociopathy and psychopathy now fall under the broader diagnosis
of Anti-Social Personality Disorder meaning that a sociopath and a
psychopath are essentially now the same thing, despite their few
differences. The term narcissist remains the same, however, and comes under the
diagnosis of Narcissistic Personality Disorder (NPD) - malignant narcissism, however, is a separate topic.
A narcissist could be considered to be a milder
form of a sociopath/psychopath due to the fact they have little or no
empathy and are often described as being in love with themselves. Narcissists do, however, suffer with an overwhelming sense of conscience.
The main difference between narcissists and sociopaths/psychopaths is
that narcissists usually exploit people in order to compulsively
portray a false self-image (and therefore require positive attention),
whereas a sociopath/psychopath would exploit people for
self-gratification (i.e. entertainment).
A psychopath would be most likely to work alone whereas a sociopath
may have a team of people to do most of their dirty work for them.
[ Image from Pixabay - Public Domain - https://pixabay.com/en/mask-drone-psychopath-terminator-153936/ ]