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