I can't go into every detail because a lot of it is personal, but I can mention some stuff.

1.He told me while I was playing assassins creed 3 how much he enjoys seeing the people get killed, now I understand liking animations but he specifically mentioned only killing.

Now that one isn't too bad admittedly but the way he said it sounded alarm bells in my mind.

1. I was once at his place when I was a kid (he's like 10 years older than me) to install a game on his pc, while there I saw he had some throwing knives and i played a bit with one, out of nowhere he mentions how he used a throwing knife to kill a dog and how the knife went like straight through the dog and how cool it was.

2. I really don't think he loves his mom at all, she is pretty rich and basically buys him everything he wants, including a house, recently an apartment and gave him her car and additionally bought him another car but he does nothing in return, but completely manipulates his mom in order for her to not share her wealth with anyone else except him.

4.He has a vendetta against my side of the family, specifically my grandma which is weird since she was always nice to him and welcomed him and fed him but I cant go into much more detail, tldr he kinda screwed us out of the previous "apartment" we stayed at and basically completely stopped his mom from helping us financially.

5.He has several children with several women including one that is 10 years younger than him and was 16 or 17 when she got pregnant and basically treats them like trash(dunno if physically abusive tho)

1. As I mentioned he has several children but only cared for the first one for a while then stopped, admittedly it was a complicated situation that one, then the one he had with the 16 year old basically doesnt exist to him, dont even know if he ever saw the kid, now he tried to live with his latest kid and the first one in his new apartment that I mentioned but the first kid didn't like it there so she stays with grandparents.