Sociopaths fascinate me; especially late-stage sociopaths.

Usually by middle-age, sociopaths have exhausted all their human relationships. Everyone in their orbit has directly or indirectly learned to avoid the sociopath, who has simply fucked over too many people.

Now it gets good. The sociopath is now starved for attention. The boredom sets in. The dopamine starts to run dry. They remember the hits that came from using to naive dopes, and it leaves them desperate to FEEL anything. They can't get that fulfillment from forging meaningful human relationships, so the late stage sociopath does the logical thing. They self-destruct with drugs/alcohol, for lack of any other source of a thrill. They usually die soon after and alone.