Here is the full list of all 15 Sonic Adventure DX achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Clear all 60 missions.
Become friends with Big.
Clear all characters stories.
Clear the Sonic story.
Become friends with E-102.
Become friends with Amy.
Become friends with Knuckles.
Get Level A on all the Action Stages by using Metal Sonic.
Get all 130 Emblems by playing Sonic Adventure DX.
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.
Become friends with Tails.