I'd say ExTP 3w2 So/Sp, 5 or 7 head-fix, 9 or 8 gut fix. I would say core-8, but an 8 that lacks empathy would be more psychopathic. Enneagram 3 pretty much reads like the mainstream pop culture definition of a 'sociopath', both supposedly wear masks and 'charm' people to get what they want.
The 9-fixer will be more cunning, chameleonic and subtle creepy, the 8-fixer will be a bit more brash and direct. Both So-Dom and the balance of Ti-Fe will make them incredibly perceptive of the emotional reactions of others; Tertiary-Fe lets them influence others emotionally, while at the same time, maintaining a sense of detachment through auxiliary-Ti. An ESTP sociopath would pick up on immediate cues as they come or use basic social manipulation, while an ENTP would probably notice some general pattern of behavior and work with that. So/Sp > So/Sx, since the former is less revealing and isn't going to be as focused on intimacy. An So/Sx sociopath could work (Tony Soprano is 8w7 So/Sx), they could play up their secondary-Sx to seem endearing, harmless and intimate, but I'd imagine they'd spread themselves too thin in the process. So/Sp's are a much more general taste.
Fictional example of an ETP 379 So/Sp sociopath: