All about one of my characters: Mhaldin

Downtrodden and in pain. Resourceful and extreme. Exceptional and deadly.
If my whole series was published and sent to stores tomorrow, Mhaldin would be the most controversial character. He is a fifteen-year-old boy with a valkyrie mother and a human father, making him a, as someone once said "male valkyrie". He does not have the usual array of powers but does share the thoughts of his twin sister, Fenera. The two are as close as peas in a pod, both willing to die for the other. His description in book 5:
"Mhaldin was slightly skinnier than his sister though this was due to his body shape and not to a lack of fitness. Actually, Mhaldin was far more athletic than Fenera and stood almost a foot taller than her. He almost always seemed to be projecting a cheery mood. While some might make others feel uncomfortable with their rough appearance or negative attitude, Mhaldin’s demeanor was such that those around him could feel positive just by looking at him even if he wasn’t more cheery than the average person. Like Fenera he was very well disciplined."
So why the idea of controversy? He sounds like a nice enough kid, right? Actually, he isn't all smiles. Religious fanatics hate him for being a male and a valkyire. He has survived 6 assassination attempts. During the course of book 5 he is kidnapped, tortured (Mhaldin is the tortured '13 year old' I refer to in the 'Eray Rated R' post, although the draft it refers to is outdated: Mhaldin no longer gets executed), and nearly killed by decapitation. When finally released, he adopts a horrifying anti-social demeanor. His ideology? The world has rejected him, therefore, he has the right to fight back. During the course of book 6 he takes a terrible revenge on those who wronged him. In the end, tens of thousands of people are killed and Mhaldin murders one too many people and joins Usor'an to escape the law. It falls to his sister (who shares his thoughts and still dearly loves him) to take him down.
Mhaldin, as I believe, pushes the envelope of what is appropriate. I do avoid excessive description when he is being tortured, but do not hold back when he is killing people (in one instance, he slaughters a keep full of unarmed bandits). Is it right to have a teenage boy pile up the bodies in the way he does: a purely anti-heroic style? Maybe it isn't.
Being a villain, Mhaldin is destined for punishment. Not even I know how this is going to end. My projected ending is to have a family member (i.e Fenera) kill him and then mourn over it but do not know exactly how it will go down (one particularly morbid version has Fenera and Mhaldin kill one another, then have their father discover the bodies). I want the scene to be perfect: a totally eye-flooding tragedy that lies at the end of a very long fall from grace.
(edit) in the Theme Songs post, when I say Mhaldin's theme is the Soccent Attack from the Transformers score, I mean the song that plays during the Michael Bay Transformers movie when Blackout attacks Soccent. This song (please don't pull it YouTube) http://www.youtube.com/watch?v=EM7SWfYSxw4