Teradata Administrator tool used to have a function to show rights held by a database.
You can also directly use SQL to query that instead of relying on the GUI tool.
Rights held by a database
select * from dbc.allrights where UserName='TestDb';
The above code snippet returns all the access rights held by database container TestDb.
Rights held by a user
For Teradata, a user is also a database. Thus you can use same SQL to query rights held by a database user:
select * from dbc.allrights where UserName='DBC';