it's a mental disorder. Sociopaths are people that don't have feelings like we do or at least not the same way we do. For example a sociopath lacks empathy unline the common person. They have various antisocial treats altho some of them have found a way to fit in with the rest of the people. They're pretty much like a psychopath, with some differences. Psychopaths are born, their brains are built differently while sociopaths are not born, they are created, usually from childhood abuse and in general abusive behaviors in their environment. They feel no fear, anxiety, empathy e.t.c Most can see you droo dead and have zero reaction unless there are people around. They are known to take advantage of others. Not all of them are evil tho, some actually do really try to fit in.
well sociopapths usually have a sad past. Like you said, doesn't justify anything. Personally i don't give an f about his past, he killed an innocent child in a really gruesome way, there's zero light in that monster. Many people have bad circumstances, mc did too but never became a monster. Sometimes it's a choice.
yeah i was being sarcastic lmao people don't care how disgusting a character's actions are as long as they're hot. they all be like "aww he must've had such a hard childhood for him to grow up to be a shitty psychopath like this i wanna give him a hug uwu" i really doubt he'd get a bad ending, they'll probably give us his tragic backstory and expect us to pity him

Dion is literally hell's spawn and has the nasty smell of sociopathy (no offense to sociopaths)