Query to get a list of contacts not tagged with a tag, but the user has multiple other tags
I don't know how this would translate to Drupal Views, but here is the SQL to do it: 

SELECT 
  contact.id
FROM civicrm_contact contact
LEFT JOIN civicrm_entity_tag et ON
  et.entity_table = 'civicrm_contact' AND 
  et.entity_id = contact.id AND
  et.tag_id = 1 /* ID of the tag you want to exclude */
WHERE et.id IS NULL;


Note that et.tag_id = 1 must be in the ON clause and not in the WHERE clause.