I assume both lists are different data sources. If yes, then do a LEFT JOIN on User ID or Username. So, 'All User Group' data source should be on the left and 'Other AD group' data source should be on the right of your LEFT JOIN.
This join will keep all users from 'All User Group' but will only bring in matching users from 'Other AD group'. All users who are not part of AD groups will appear as null.
Let's assume Username1 is from All User Group table while Username2 is from Other AD group.
Create this calculated field [Users not in AD Group]
IF ISNULL([Username2] THEN [Username1] END
Hope this helps.