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