Another one I thought of: he used the strategy of constantly involving himself in conflict, and when he destroyed Ja Rule's life the strategy worked to perfection. But then I think he misapplied the principle by not choosing his enemies correctly. The great thing about ending Ja's career was that by going at Ja, he was able to more strongly define himself. Ja was a studio gangster, 50 was the real deal. By obliterating Ja Rule and Irv Gotti, he established and defined his identity.
When he went at Jay, Fat Joe, and The Lox it didn't make as much sense. Those are street credible guys. By going at them it doesn't help define who he is. That's when he just started to seem like a publicity stunt type dude. It actually served to hurt his credibility. It fukked him up in the long run, because by the time he found the perfect target in Rick Ross, the ultimate CB4 studio mafioso, his credibility had already been shot, and his beef seemed contrived.
That leads me to the the next point, he stopped picking opponents that he could handly defeat. His ego went out of control. When he challenged Kanye to the sales battle, he was already losing steam, while Kanye was on his way to legendary. It was a stupid fight to pick and he got embarassed, further damaging his credibility.