I'm searching for fanfictions where Harry is a sociopath and growing up with Tom Riddle. Preferably finished but if they're well written I don't mind unfinished stories too much.

 

You're basically looking for cannon harry with a sibling twist. Someone had a remarkable chart about the similarities between Harry and Tom, characterization wise but I've forgotten who. Let's ignore the surface similarities for a moment, you basically have two very stubborn characters with opposing drives that bring them into conflict. If you want them to work together they have to either A.) Face a situation where it benefits them put aside their differences. B.) Actually, consciously put aside their differences (Unlikely)

 

Do you mean raised by Voldemort, or somehow gets transported back to the 20s and is raised alongside Voldemort (or vise versa). Because there are a lot of the former (mostly shit or slash) and not much of the latter (but probably mostly shit or slash).

I honestly have a deep, unrepentant hatred of most stories that give Harry a different childhood (because most of them are shitty hurt/comfort stories, angst, or family fluff. All of which make me want to stab someone's eye out with a fork).

As for a sociopath!Harry... it might be difficult to find a combination of the two, so... assume most of these only have the first part.

The Darkness Within by Kurinoone is one of the former, and it's pretty much the only one I can think of that doesn't suck. Features a Harry that is a sociopath. That said, it's a redemption fic.

Hit the Ground Running by Tozette features a Harry who is able to communicate with the Horcrux in his head. His relationship with Horcrux!Tom is the focus of the story. As a warning, many (me included) think the ending was absolute shit.

Lily and the Art of Being Sisyphus by The Carnivorous Muffin has a fem!Harry who can communicate with her horcrux, and ends up getting paired with Voldemort somehow (I put reading this on hold a while back, so I have no idea how this works). Their relationship is only one of many important points of the fic. It's a bit wacky, so be warned.

Thunderstorm by T3t is... kind of like your second premise. Features a Harry/fem!TR pairing that's somewhat interesting. They both start out at sixteen, so it's not exactly growing up together, but...

It's not exactly what you're looking, but check out this thread for some stories that might be up your alley.

As for sociopath!Harry... this thread from 2011 probably has something you're looking for.

 

Or do you mean the scarcrux talks to Harry and ends up being his "friend" as a child?

 

Thanks for your answer, Pure Infinity. Actually, I meant a story where Harry grows up with Tom Riddle somehow influencing him, so really both of your suggestions. Unfortunately I experienced the same when searching, I had hoped to have just missed the good ones. I've already read all of your recommendations, liked some more than others (have to say though: Kurinoone's trilogy is awesome!). I will check the links out next, maybe I'll find something