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.
Become friends with Knuckles.
Become friends with Tails.
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.