Here is the full list of all 48 Sonic Forces achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Completed 10 Daily Missions
Collected a total of 100,000 rings. (All Rings held at the end of the stage will be counted.)
Collected all parts
Completed all Challenge Missions
Collected all Wispons
Achieved highest honors with all races
Collected all Silver Moon Rings in Shadow's Story.
Collected all Number Rings in Shadow's Story.
Collected all Red Star Rings in Shadow's Story.
Collected a total of 50,000 rings. (All Rings held at the end of the stage will be counted.)
Completed 5 Daily Missions
Completed 10 SOS Missions
Used the Closet
Defeated 10,000 enemies
Collected 500 parts
Cleared all EX Stages
Cleared all Secret Stages
Collected 30 Wispons
Collected all Silver Moon Rings
Collected all Number Rings
Collected all Red Star Rings
Completed 5 SOS Missions
Defeated 5,000 enemies
Utilized the Rental Avatar function
Created your second Avatar
Restored peace to the world
Defeated Infinite
Equipped a part in every slot
Turned the tide of the conflict
Drove off Infinite again
Liberated a world
Collected 10 Wispons
Collected a total of 10,000 rings. (All Rings held at the end of the stage will be counted.)
Completed your first SOS Mission
Achieved a soldier's highest honor
Collected 100 parts
Drove off Eggman
Made it into the rankings
Drove off Infinite
Collected Silver Moon Rings three times
Collected Number Rings three times
Defeated 1,000 enemies
Collected 50 parts
Defeated Zavok
Changed Wispons for the first time
Completed 3 Daily Missions
Created an Avatar
Cleared Stage 1