You've had some good suggestions so far - but nobody has yet mentioned this one. BLAME.
Often this happens because of us, because we are trying to teach consequences, and with some kids (especially the Pervasive Developmental Disorder (PDD)-ish ones who are focussed on identifying the 'rules' that define the world around them, and who pick up on perceived patterns FAST) they focus on blame and try to find where to assign the blame for what has gone wrong. Add in to this the resentment and "it's not my fault" of a typical teen and you have a recipe for what you describe.
First - go back and think about your own responses to him now and in the past. Also to your other kids. Also think about other influential people in his life - teachers, other family members, close friends (if any). Do they also focus on blame to any extent?
It's okay if you find that you have. It is natural, often appropriate to a certain extent. But some kids begin to focus on it TOO much, and there we have to intervene.
Next - change your own behaviour. This is most important. When something bad happens to you, or he does something bad and the consequences are unpleasant, don't focus on fault, just focus on "bad things happen sometimes". If you can find enough "bad things happen sometimes and it's not always about blame," then where it IS connected directly as a consequence, let him know about the connection, where it is obvious. But otherwise, leave it. Work on emphasising that often it's not about blame. Instead, he should focus on how he can precent it next time. It's STILL not about blame, but it can be about how I can improve. Fumbled the ball at the game? Maybe get in some more passing practice to hone the brain pathways that help with hand-eye coordination.
Also linked to this is - sometimes the ball just goes astray. To assume the ball hitting him was directed towards him deliberately, is to assume that the person kicking the ball has skills better than David Beckham AND feels sufficient resentment towards him to make them want to waste such skill on him. Frankly, he is not that important, and the ball-kicker cannot be that skilled.
The trouble is, the more you try to convince him that it wasn't deliberate, the more he will be focussed on "well, if HE isn't to blame, who is?" Still blame-focussed, so he needs to get right away from blame, before worrying about who is responsible.
Another angle - if there IS a chance the ball was aimed at him deliberately, it is only a chance. When he retaliates, it is 100% deliberate and that is out of balance with the original incident. This means that the blame-focussed other kid is going to be deliberately aiming at difficult child next time, which perpetuates it. It also builds a lot more anger and resentment in difficult child than is healthy.
Focussing on blame makes you angry and has you increasingly focussing on unfairness and more blame. This can really consume you and if YOU do it, this passes onto your children and sets them up for a life of avoiding personal responsibility.
It can be a bigger task than you realise, to change from blame-focussed to "sometimes it just happens that way." It can be a very hard lesson especially for kids who really need to understand the cause and effect in the world; the alternative, chaos, can be too scary. But this lesson, when learned, can make a world of difference in everybody concerned.
We each as parents harbour a lot of resentment in being saddled with a difficult child kid. When that kid misbehaves, often our resentment comes to the surface and we find ourselves saying, "See? I told you that would happen if you didn't stop doing it! Serves you right!"
We need instead to stay calm and ask the child, "What happened?" "How can you contribute to a better outcome next time?"
Especially at first, he will try to duck responsibility. "HE did it! Not me! I was minding my own business..." and you need to step in and say, "Stop! This isn't about blame. If you want to only concentrate on blame, you have to understand that chaos theory means a butterfly could flap its wings in Japan and a cyclone happen in the Caribbean - everything is connected, but not always responsibility."
Chaos theory might help, actually. It's a way of saying that something happens here - a tree falls over from a gale, for example - an animals become homeless. More animals invade your garage during cold weather, and the favourite baseball mitt stored in the shed gets chewed by some crittur. All because a tree blew over in the woods - but the tree is not to blame. What could have been done to protect the baseball mitt? Maybe don't keep it in the shed. But is the owner of the mitt to blame for it being chewed? Not really, It just happened. He could have improved the outcome by storing it more carefully over winter and maybe he can learn from the experience. But he can also take comfort that some creature had a better chance of survival, because the baseball mitt gave it some nourishment, briefly.
There are many ways to look at a situation. I suggest that a difficult child focussed on blame needs to be deflected from it and taught that in life, sometimes bad things happen for no reason. But even then, we can learn from it and remember, in order to produce a better outcome next time.
Marg