Going through some article, it seems the differences between the descriptions for sadistic personality disorder and psychopathy is minimal, if at all existent. In the first article it appears the only difference is a propensity for physical violence. In the second article, the high correlation between psychopathy and physical violence is debunked as a myth.
Given the similarities between the two conditions;
What is the real difference between an individual with Sadistic Personality Disorder and Psychopathy?
What are the real facts correlating violence in psychopathy?
The excerpts are provided below:
The Sadistic Personality disorder is characterized by a pattern of gratuitous cruelty, aggression, and demeaning behaviors which indicate the existence of deep-seated contempt for other people and an utter lack of empathy. Some sadists are "utilitarian": they leverage their explosive violence to establish a position of unchallenged dominance within a relationship. Unlike psychopaths, they rarely use physical force in the commission of crimes. Rather, their aggressiveness is embedded in an interpersonal context and is expressed in social settings, such as the family or the workplace.
This narcissistic need for an audience manifests itself in other circumstances. Sadists strive to humiliate people in front of witnesses. This makes them feel omnipotent. Power plays are important to them and they are likely to treat people under their control or entrusted to their care harshly: a subordinate, a child, a student, a prisoner, a patient, or a spouse are all liable to suffer the consequences of the sadist's "control freakery" and exacting "disciplinary" measures.
Sadists like to inflict pain because they find suffering, both corporeal and psychological, amusing. They torture animals and people because, to them, the sights and sounds of a creature writhing in agony are hilarious and pleasurable. Sadists go to great lengths to hurt others: they lie, deceive, commit crimes, and even make personal sacrifices merely so as to enjoy the cathartic moment of witnessing someone else's misery.
Sadists are masters of abuse by proxy and ambient abuse. They terrorize and intimidate even their nearest and dearest into doing their bidding. They create an aura and atmosphere of unmitigated yet diffuse dread and consternation. This they achieve by promulgating complex "rules of the house" that restrict the autonomy of their dependants (spouses, children, employees, patients, clients, etc.). They have the final word and are the ultimate law. They must be obeyed, no matter how arbitrary and senseless are their rulings and decisions.
Most sadists are fascinated by gore and violence. They are vicarious serial killers: they channel their homicidal urges in socially acceptable ways by "studying" and admiring historical figures such as Hitler, for instance. They love guns and other weapons, are fascinated by death, torture, and martial arts in all their forms. 1
In another discussion the idea of a psychopath being typically violent is dispelled as a myth:
All psychopaths are violent. Research by psychologists such as Randall T. Salekin, now at the University of Alabama, indicates that psychopathy is a risk factor for future physical and sexual violence. Moreover, at least some serial killers—for example, Ted Bundy, John Wayne Gacy and Dennis Rader, the infamous “BTK” (Bind, Torture, Kill) murderer—have manifested numerous psychopathic traits, including superficial charm and a profound absence of guilt and empathy. Nevertheless, most psychopaths are not violent, and most violent people are not psychopaths. In the days following the horrific Virginia Tech shootings of April 16, 2007, many newspaper commentators described the killer, Seung-Hui Cho, as “psychopathic.” Yet Cho exhibited few traits of psychopathy: those who knew him described him as markedly shy, withdrawn and peculiar. 2
1 Sadistic Personality Disorder "Personality Disorders Revisited" (450 pages e-book) By: Dr. Sam Vaknin
2 What "Psychopath" Means It is not quite what you may think By Scott O. Lilienfeld and Hal Arkowitz
note: I post a run of related questions, please do not be disturbed by the content.