Although I mentioned in a previous post that I think people can have happy and successful relationships with sociopaths and narcissists, I do think that there are ways to manage their behavior or to help them manage their own behavior. Here is my response to the previous post:
Yes, your friend sounds like a sociopath or narcissist. You should actually be hoping for sociopath at this point, because they are much easier to reason with. Narcissists are completely self-deceived. They don't think they are different than empaths, just better: less likely to be duped, a leader among mere mortals, that type of thing. They like situations where other people are dependent on them, whereas sociopaths like people to be enslaved to them. Narcissists are motivated more by a need to be loved and admired (acceptance/respect), sociopaths are motivated by a need to be respectfully feared and in control (power).
Your friend sounds like more of a narcissist than a sociopath from your description. I've found that most sociopaths, like people with Asperger's, are aware of their condition, even if they may not know what to label it. Because your friend is refusing to admit to himself that his personality fits the Antisocial Personality Disorder spectrum traits, that suggests to me that he is a narcissist. He could also be a particularly low-functioning sociopath, meaning poor self-awareness and poor impulse control. Those type of sociopaths are the ones that go to prison, so you are justifiably concerned for your friend.
Either way, the "treatment" I would suggest is the same: redirection and distraction. This info is taken from a poorly edited book with some decent information called Just like his Father?. It discusses how to parent sociopathic children, but the principles can apply to everyone dealing with a sociopath.
The book describes how to teach impulse control. When children are preverbal (before a child can understand and use words), the only impulse-control tools are redirection and distraction. "Redirection is the creation of an appropriate setting for the expression of impulses. Distraction is the process by which attention shifts away from undesirable impulses." An example of redirection is a child who wants to play with your car keys or phone. You don't want the child to play with those objects because he may break or lose them. You can redirect the child by giving him fake keys or a toy phone. "By providing your child with substitutes, you acknowledge his desires as legitimate, set limits, and teach him to direct himself in a way that is productive rather than destructive." An example of distraction is when a parent tries to "distract a crying child by cuddling him and making funny faces. In this exercise, the child learns to shift attention from a negative feeling state to a more positive one."
After children become verbal, most toddlers use language to strengthen their impulse control. "Watch as your child picks up the previously mentioned keys or cell phone while repeating to himself 'don't touch mommy's keys' and 'don't play with mommy's cell phone.' Commanding himself to put the objects down requires a great deal of effort. You may notice that the commands your child gives himself are identical to the ones you have given him. . . if you have witnessed this process, you have observed the building blocks of conscience . . . once the conscience is fully formed, the process of verbal command over impulses happens automatically. The child can stop himself without thinking about it."
I would say that most high functioning sociopaths are stuck at repeating to themselves "don't touch mommy's keys" with a great deal of effort. As they routinely do this in a particular area (e.g., don't tell people they're fat), they may develop a habit and not have to think so much about it anymore. But obviously if you have a friend whose lack of impulse control is leading to self-destruction, the friend probably isn't even at the don't-touch-mommy's-keys stage. That's why i suggest redirection and distraction, if possible.
Your friend has legitimate needs and wants, and you want to be sure to address those and not alienate him by criticizing his basic self/needs: "By providing your child with substitutes, you acknowledge his desires as legitimate, set limits, and teach him to direct himself in a way that is productive rather than destructive." You need to find out what his needs are, and cater to those needs in non-destructive ways, or teach him to do that for himself.
I don't know what non destructive substitutes may be for your friend, but you should probably prioritize in your mind which of his less-than-desirable behaviors are the most harmful to him, then focus on those. Otherwise, it would be like your friend trying to quite heroin, alcohol, sex, porn, cutting, smoking, and bulimia all at the same time. Not possible. You have to prioritize.
I suggest your friend reads The 48 Laws of Power. It's sort of a sociopath's bible about how to cultivate power, but I think it can also really help narcissists become more self-aware and sociopaths have more impulse control.
Hope this helps.