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