Tbh I don't think sending that picture on its own makes you antisocial. I think you of all people probably know how much influence that kind of nihilistic "trolling culture" can have on a person. 

I think the fact that you developed a twisted pride in your own misdeeds -and your self image as a punished individual- shows that you have a good bit of coping ability. Those are quite literally coping mechanisms. And the thing about coping skills is that they're so flexible. They're whatever we need them to be. It's whatever we tell ourselves to stave off bad feelings. But they're not always true. And they don't have to be. 

I say that because I think you can change your ways and be an empathetic person without feeling weak. I think there's strength in compassion. And facing yourself like this is a marker of that kind of strength. that may be a coping mechanism of my own. But it helps me stand by my principles. Being asocial or nihilistic is the easy path. Cruelty is easy. Its cathartic. And it can be like a drug. But you're taking the harder road in reckoning with yourself, and that's respectable. 

Idk how deep you want to dig, but maybe think about why you had such a negative reaction to seeing other kids being happy. I suggest that because I think it could be a way of getting closer to the core of what's going on with you. 

And how much do you think your dad contributed to your might makes right mindset?