Best way to quickly and effectively drop a database and delete all files?
Unless you are in the context of the database, you can't ensure you are the only one using it. Also, don't use batch separators. Run it all as a single batch.

Use AlwaysEncryptedSample;

ALTER DATABASE AlwaysEncryptedSample SET SINGLE_USER WITH ROLLBACK IMMEDIATE;

Use master;

DROP DATABASE AlwaysEncryptedSample;