CheatCodes.com has the complete list of all Sonic & Knuckles Achievements and Gamerscores for X360, including all secret Achievements. All official X360 achievements for Sonic & Knuckles as of Wednesday May 6, 2015 are shown below, or you can print out our Printable Achievements Checklist that shows all Sonic & Knuckles Achievements and Gamerscores in a simple quick-reference format.
Complete the game as Sonic.
Complete the game as Knuckles.
Earn a Continue in either a Bonus or Special Stage.
Collect all seven Chaos Emeralds.
Collect a Chaos Emerald.
Finish the Lava Reef Zone.
Finish the Sandopolis Zone.
Finish the Flying Battery Zone.
Finish the Mushroom Hill Zone.
Collect 100 rings.
Start the game once as each character.
Enter a Bonus or Special Stage.