Sonic never knew how evil Eggman truly was. After his defeat in Forces, and after Classic Sonic left, Eggman saw the Phantom Ruby had energy left. He used it as a last resort against Sonic, and it worked. The blast hit Sonic square in the chest, and he fell backwards, right in front of his buddy Tails, and all of his friends. He knew it wasn't fatal, seeing as how he was still alive, but he looked up once more, to see Tails in tears as the world faded to black.