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