In which region have the most 1-star reviews been done?
most 1-star reviews refers to MAX(COUNT(stars = 1));
SELECT T3.Region FROM reviews AS T1 INNER JOIN district AS T2 ON T1.district_id = T2.district_id INNER JOIN state AS T3 ON T2.state_abbrev = T3.StateCode WHERE T1.Stars = 1 GROUP BY T3.Region ORDER BY COUNT(T3.Region) DESC LIMIT 1