When you need to remove subscribers from a WordPress server and there are too many to user the web interface, use this SQL to delete them and then cleanup the associated metadata.

RemoveSubscribers.sql

# Wordpress Management
# Remove all subscribers using SQL Query

# Delete all of the users with Subscribe capabilities
DELETE FROM wp_users WHERE ID IN ( SELECT user_id FROM wp_usermeta WHERE meta_key = 'wp_capabilities' AND meta_value LIKE '%subscriber%' );

# Cleanup the meta (bonus! it cleans up all meta not associated with an existing account)
DELETE FROM wp_usermeta WHERE user_id NOT IN ( SELECT id FROM wp_users );