1. Beat Team Dark’s story in Hero Mode. This is the easiest method to unlock Super Sonic. Once you’ve beaten the boss, you’ll be able to choose Super Sonic as a playable character.
2. Collect all 101 emblems. This is a much more time-consuming method, but it’s still possible to unlock Super Sonic. Once you’ve collected all 101 emblems, you’ll be able to choose Super Sonic as a playable character.
3. Unlock Super Sonic in Adventure Mode. Beat the final boss, Metal Sonic, and collect all of the Chaos Emeralds. Once you have all 7 Chaos Emeralds, head to Angel Island and use them to transform into Super Sonic.