Sonic Adventure 1:
""https://www.reddit.com/r/SonicTheHedgehog/comments/16sxwuu/what_counts_as_100_completion_in_sonic_adventure/
So for 100% completion, as i would put it, you would need...
All emblems in the Adventure field
All Characters 100% including the final story
All emblems in each characters stages in trial mode (this includes all A, B, and C missions)
All emblems in the sub missions (this includes any tornado acts, snow/sand boarding, and twinkle park circuit)
All Chao races
Total Emblems: 130
Doing all of this will grant you the bonus unlock: Metal Sonic in trial mode for Sonic stages""
- from the reddit post
Sonic Adventure 2:
https://steamcommunity.com/sharedfiles/filedetails/?id=312189613
Have you noticed that every time you finish a level for the first time, a little symbol of Sonic appears with a number underneath him? That is called an Emblem, and there are 180 of them total in the game. They can come from all types of different activities, such as finishing story mode, finishing all missions for a character, and even just doing stuff with your chao! In this guide, I plan to list out all of the Emblems you can obtain (and the minimum on how to obtain them). Be warned, if your after all 180, it will take quite some time (even for a veteran player!)
-from the steam post
yeah apparently 100% these games are pretty difficult. idk tho never played them