sorry im thinking about half man again. niall was long doomed but he wanted to live so so bad by the end. he knew what was coming and could hear the countdown from the moment ruben stopped laughing but he still fought and he almost made it. ruben just kind of accepted that his life was over and made sure to drag niall down with him. niall had so much going for him but in the end he still lost anyway because ruben never cares what he loses as long as he can brute force his way to some superficial victory all because he cant stand to have his masculinity challenged.
niall eventually tried to work through things and seemingly was able to do so well enough that he reconciled with several people he wronged throughout his life. ruben doesnt even want to be capable of that, so he never will be. niall was living proof that anyone could change, and ruben spit in the face of that, rejecting all the chances he got to alter the path he was on until the bitter end just so he didnt have to admit he was wrong to begin with.
everything ruben does has an excuse; thats all it's been his whole life: excuses. he cant help it, hes sick, its because of his father, everyones wrong about him, they just dont want to understand him. niall never had that luxury, even though some of the same excuses could have been used for him by the end. he tried, but no one else was ever willing to entertain that from him the way maura and lori and niall himself were for ruben.
they were both mistreated, they both had successes and failures. but niall eventually learned to grow up, and ruben was a scared, angry child in a man's body until the end. i think ruben was jealous of niall for a lot of reasons, though he'd swear he had no reason to be, and that's what ultimately killed them both. ruben couldn't stand to see him succeed where he failed, not when he'd wronged him—conveniently ignoring how his own selfish actions and abusive behaviors already almost killed niall in every way possible.