Here is the full list of all 40 Sonic Frontiers achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Viewed all Side Stories on Ouranos Island.
Viewed all Side Stories.
Performed Phantom Rush 50 times, outside of the training simulator.
Defeated all enemy types.
Defeated all guardian types.
Defeated the final threat and completed the main story.
Defeated the Titan and completed the main story on Ouranos Island.
Raised Ring Level to MAX.
Raised Speed Level to MAX.
Repaired all Portals on Ouranos Island.
Raised Defense Level to MAX.
Completed all Challenges on Ouranos Island and fully revealed the map.
Raised Power Level to MAX.
Unlocked all Skills.
Defeated the Titan and completed the main story on Chaos Island.
Viewed all Side Stories on Chaos Island.
Completed all Challenges on Chaos Island and fully revealed the map.
Repaired all Portals on Chaos Island.
Defeated the Titan and completed the main story on Ares Island.
Viewed all Side Stories on Ares Island.
Gathered 200 Koco.
Repaired all Portals on Ares Island.
Earned 100 Purple Coins.
Landed all catches at one fishing spot.
Defeated the Titan and completed the main story on Kronos Island.
Viewed all Side Stories on Kronos Island.
Completed all Challenges on Kronos Island and fully revealed the map.
Completed all Challenges on Ares Island and fully revealed the map.
Spoke with Elder Koco for the first time.
Spoke with Hermit Koco for the first time.
Destroyed 100 breakable objects.
Encountered a starfall for the first time.
Repaired all Portals on Kronos Island.
Completed the fishing tutorial.
Performed a Phantom Rush for the first time, outside of the training simulator.
Completed the Kronos Island tutorials.
Completed all Missions in one Cyber Space area.
Achieved Rank S time, for the first time in a Cyber Space area.
Activated a Power Boost for the first time.
Defeated a guardian for the first time.