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