Full list of all 15 Sonic Adventure achievements worth 250 gamerscore. It takes around 20-25 hours to unlock all of the achievements in the base game.
The base game contains 12 achievements worth 200 Gamerscore, and there is 1 DLC pack containing 3 achievements worth 50 Gamerscore.
Become friends with Tails.
Become friends with Knuckles.
Become friends with Amy.
Become friends with E-102.
Become friends with Big.
Clear the Sonic story.
Clear all characters stories.
Get Level A on all the Action Stages.
Get all Emblems of the Sub Games.
Get all Emblems of the Chao Race.
Get all Emblems in the Adventure Field.
Get all 130 Emblems.
Get all 130 Emblems by playing Sonic Adventure DX.
Get Level A on all the Action Stages by using Metal Sonic.
Clear all 60 missions.