Maybe AFO's heart is full of hate for 2nd and hero society because they caused Yoichi's death? But I think Hawks has a minor point, AFO could never steal OFA after all those years because hate is not the strong emotion he has for Yoichi and he sees OFA as Yoichi's quirk. His love for his younger brother completely shadows his desire to acquire OFA.
Im a firm believer of the theory that afo killed his brother, but it was an accident and it was the 2th he actually wanted to kill, but yoichi pushed him out of the way. It explains afos immense hate for the 2th. But I think that afo actually hates nothing more then HIMSELF! Remember he was inspired after darth vader and vader hated nothing and no one more then himself, because of his believe that he killed his wife and his unborn child!
The thing is, do you remember how hawks, endeavor and bj once talked in a car about why afo is not able to steal ofa himself and why he needs an other persons hate for that? Back then they had the theory that afo is unable to feel any kind of human emotions like hate or love because of his "lack of heart". But we know for a fact that afo IS ABLE to feel that. He hates all might! He hates the 2th! He hates nana! And he still loves his brother and if we consider the dfo hints he also loves his family! (Not saying in a healthy way).
So you are absolutely right. Afo needed a new body full of never ending hate, to be able to steal ofa, because he himself is not able to. His love for yoichi is bigger then his desire to steal ofa and his hate for himself.
There is just one thing Im curious about. Garaki tells afo in this chapter that he wishes his heart to be free of all hate and thats weird if we consider that with hate he would be able to steal ofa himself! So why does garaki wish that for him. He also gave him some weird compliments about how he loves his eyes, smile and voice. As if he tried to cheer afo up. To make him feel better about himself. So my theory is that garaki is aware about HOW MUCH afo actually hates himself and that he suffers (vaders hate made him suffer too), and wishes for him to let go of that hate. Maybe THATS how izuku can reach him? If dfo is true and izuku reaches out to his father, wanting him to come home with him (I mean the todorokis want the same with dabi despite all his crimes), afo maybe is able to finally let go of his hate, because his family wants him back? Something he would never believe, because even his own brother wanted him to stay the fuck away from him? (I mean, absolutely valid wish).
Seriously we really need afos backstory. The more I see of that guy, the more he gives me hardcore past trauma vibes! What the hell happened to him?