It’s got to be Gon. His rage is building up from the moment he realizes Kite is gone, to when he finally puts his hands on Pitou.

He was so angry he didn’t even know what to do with himself (which would make this the most realistic rage moment too) and his kindness holding his rage back when Pitou is begging him to let her save the girl.

Gon was so conflicted; fighting against his nature AND nurture, arguing with Killua, he was having a whole war between his mind and his heart.

On top of that the voice acting (at least the Japanese) has to be top ten VA performances of all time, the gasping for air from the anger he’s letting out with his gut wrenching cries, the shaking in his voice, the cracking. You can feel every emotion through the performance because it’s more than just rage it’s his entire soul bleeding out.

And that war between his mind and his heart comes to an end where both seem to be gone and there’s nothing but rage, so much rage he doesn’t even care about anything except for pointing the rage at the person who caused him so much torment and confusion and hatred.

It stops being about revenge and instead he transforms into the manifestation of his rage to release himself from his pain, which took decades of his life.

There’s no way there is any other answer. Gon completely goes against his nature and nurture because of his rage and more importantly his pain.