Most comman scenario which we face on everyday basis is to fix the orphan database users at the database level. You need to go to each database and fix the orphan users at the each databases.
If you have hunderds of databases in the enterprise level environment , it is very hard to do that. I wrote the script
Thanks to the previous contributor SM who have wrote the orphan users script. I made modification to the scripts to go into each database and check the orphan users.