What is the Customer Name who has the most policies listed ?
SELECT t1.customer_name FROM customers AS t1 JOIN customers_policies AS t2 ON t1.customer_id  =  t2.customer_id GROUP BY t1.customer_name ORDER BY count ( * )  DESC LIMIT 1
Customer Name who has the most policies listed refers to the name associated with the MAXIMUM number of entries in customers_policies, grouped by customer and ordered in descending order by count.