@Bramia
Yes, it is not the only way, but it is one of the best, and it is among the "not normal".
But what do you mean by "fix his attitude"?
There are objectively close to no problems with being a psycho, the only thing who think psychopathy is a problem is society because a gear that doesn't fit in it's place is worthless/dangerous.
From an objective point of view (with Wikipedia's definition of psychopathy):
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Antisocial behavior means he doesn't give a shit about society, so if he has to do something he will do it even if it's immoral. He already has this advantage compared to the average guy's scared of doing anything that might attract the law.
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Impaired empathy: no unconscious restraint of hurting someone since he will not place himself in their place, he can aim for the eyes or the crotch, for example. And also he will not put himself in danger in order to help someone.
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Impaired remorse: no regrets. I don't need to say more. No mental demons, especially when you can live for hundreds of years, and therefore reaching eternal life is possible.
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Boldness: acting when it is needed to act, no worrying for hours before acting.
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Disinhibition: impulsivity and poor risk management, which is indeed no beneficial.
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Egotistical trait: how to keep your mental health when you are in a world where there are geniuses and sons of heaven everywhere? Putting oneself as the center of everything. No matter what others are capable of, in the end, you are still you, and no one is better at being you than you.
And after this long list, MC does not seem, in my opinion, completely psychopathic. I see it more like a developed logical and pragmatic mind, like a robot, he acts with the best course of action to complete one's goal. In order to win, disable your opponent (before taking his life for death battle): breaking the ankle of the woman I forgot the name. And he can even switch on-off the pragmatic side of him if he's in a state of combat or in "civil mode" (he didn't seem that dangerous when he was interacting with the old guy for the Body of Tumultuous Gold), which shows a great deal of self-control, which contradict with Disinhibition of psychopathic behavior.
So no, I hope he doesn't change and stay as being himself.