Let's be honest. Sometimes the best books can be problematic. Or have problematic villains. And sometimes people like the villains despite them being problematic. Riko Moriyama is one of those villains. Despite being an awful awful person I have seen numerous fanfics on ao3 (the only place I can find any good AFTG fics sadly) that have him paired with one of the good characters or being treated like a sad lost child. He's not. I promise you HE IS NOT!
In the series Riko has; murdered a character and faked that they had an overdose, tortured numerous people, paid a r*pist to kill one of his previous victims, paid of a therapist to reenact aforementioned r*pe while aforementioned victim was recovering from the previous incident, and more that I can't bare to remember.
In Nora's extra content she has said that Riko has broken Jean's fingers numerous times and even ordered him to break them himself as well, pushed Jean down the stairs, waterboarded him, and has had other Raven's r*pe Jean. Nora says that "Riko will not engage in anything homosexual himself, but he is not above inflicting sexual trauma on others via others". And these are just the things she listed on tumblr. I'm sure there is more that he has done to Jean and other Ravens.
He broke his adopted brother's hand just because he couldn't stand being seen as second best for crying out loud. Stop acting like he's a misunderstood child.