The next chapter has Sonic, Rainbow Dash, and the Princesses going up against The FinalHazard, with Sonic helping Rainbow Dash perform a Sonic Rainboom.
Then there's the battle between Sonic and a Brainwashed and Crazy Silver in the next chapter, with the power of a Chaos Control with two Chaos Emeralds freeing Silver and restoring Appleloosa.
As bad and evil Eggman is, his speech in middle of Chapter 16 was awesome. First he pointed out flaws in Celestia's thinking, then in Mane 6's thinking (minus Twilight who was driven to Heroic BSOD with Eggman striking on her insecure mentality, just as Mane 6 was firing Elements of Harmony). Not so much Friendship is Magic as you think, eh, ponies?