I agree that Voldemort is very hard to type, to the point where he might be untypeable. Also, if he is a sociopath, then that makes him even harder to type. But let's break down what we know about him. He was obsessed with power, yes, but also, he was obsessed with hidden and forbidden knowledge, and ancient and dark magic. This obsession for knowledge points to a 5-fix, perhaps (unhealthy). Also, what do we know about Tom Riddle? A very charming model student, who had all the teachers and students wrapped around his little finger. But no one knew the true Tom Riddle or saw through the masks (except Dumbledore). He could manipulate almost anyone. Also, he removed anyone who got in this way, with a brutal efficiency. I think this points to a 3-fix (unhealthy). I'm not sure about a gut-fix for him...definitely not 9 lol. Possibly a 8. From the books, Dumbledore told Harry that Voldemort always wanted to do everything on his own, and unlike Harry, Voldemort never sought to make connections, preferring to rely on himself.
So I see Voldemort/Tom Riddle maybe core-3 (3w2) 8w? 5w4, or maybe 8w? 3w2 5w4.
(And yes, as I deconstruct this, I have deconstructed my own tritype as Voldemort's, lol. Completely unintentional I assure you.)