This is the hardest achievement in the game, don't take this easy.
You have to beat every boss as Super Sonic, that means at the last hit you have to be Super Sonic. It's a big mistake to turn into Super Sonic directly after collecting 50 rings.
You also have to perform a Rolling Combo in 2 boss fights, That means you have to hold 50 rings up to the end of the boss fights in Oil Desert and (!) in the final boss fight.
I don't have much tips for you to perform that, cause I needed about 2 hours for the final boss ... but I made a video guide for this, I hope that helps you.
I'm not sure about Death Egg II Act 1, maybe you need this, too. So I also made a video for that.
Enjoy that and good luck!
(Sorry for bad english, I hope it's okay. :P)