Which user has done the most review on a business attributed to delivery?
the most reviews refer to MAX(business_id) where attribute_name = 'Delivery';
SELECT T3.user_id FROM Attributes AS T1 INNER JOIN Business_Attributes AS T2 ON T1.attribute_id = T2.attribute_id INNER JOIN Reviews AS T3 ON T2.business_id = T3.business_id WHERE T1.attribute_name = 'Delivery' GROUP BY T3.user_id ORDER BY COUNT(T2.business_id) DESC LIMIT 1