After Tails, Knuckles, Silver, Shadow, Rouge, Amy, and Omega gather the emeralds, Elise gives Sonic a kiss which allows him to transform into his super form who transfers some of his powers to Shadow and Silver, and together they defeat Solaris.
Knuckles, Silver, Shadow, Rouge, Amy, and Omega gather the emeralds. This is after Tails. They defeat Solaris.