How to Delete Restoring Database
RESTORE DATABASE dbname FROM DISK = 'dbname .bak' WITH REPLACE, RECOVERY --force restore
RESTORE DATABASE dbname WITH RECOVERY
REPLACE Overwrite the existing database, do it only if you are sure you want to override your existing database as you mentioned you dont care to delete it
RESTORE WITH RECOVERY is the default behavior which leaves the database ready for use by rolling back the uncommitted transactions. Additional transaction logs cannot be restored.
That should bring the database online. Then you can delete it & try again.
Best way as i have done with this problem is write this command 'drop database [database name]' and then create new one with same name and then restore database from another .bak file because .bak file is corrupted or faulty.