Full list of all 23 Sonic The Hedgehog achievements worth 1,000 gamerscore. It takes around 60-80 hours to unlock all of the achievements on Xbox 360.
You have Received all Gold Medals of Soleanna.
You have Achieved S Rank on all ACT Missions.
You have Achieved S Rank on all Silver ACT Missions.
You have Cleared all Silver ACT Missions.
You have Achieved S Rank on all Sonic ACT Missions.
You have Received all Silver Medals of Soleanna.
You have Achieved S Rank on all Shadow ACT Missions.
You have Learned all Sonic actions.
You have Achieved S Rank on all Last Episode.
You have Cleared all Shadow ACT Missions.
You have Cleared all Sonic ACT Missions.
You have Achieved Rank S on all Silver TOWN Missions.
You have Achieved Rank S on all Shadow TOWN Missions.
You have Cleared all Silver TOWN Missions.
You have Cleared all Shadow TOWN Missions.
You have Achieved Rank S on all Sonic TOWN Missions.
You have Cleared all Sonic TOWN Missions.
You have Cleared Last Episode.
You have Cleared Shadow Episode.
You have Learned all Shadow actions.
You have Cleared Silver Episode.
You have Learned all Silver actions.
You have Cleared Sonic Episode.