Which country has the most number of suppliers whose account is in debt?
country refers to n_name; the most number of suppliers whose account is in debt refers to MAX(SUM(s_acctbal < 0));
SELECT T.n_name FROM ( SELECT T2.n_name, SUM(T1.s_acctbal) AS num FROM supplier AS T1 INNER JOIN nation AS T2 ON T1.s_nationkey = T2.n_nationkey WHERE T1.s_acctbal < 0 GROUP BY T2.n_name ) AS T ORDER BY T.num LIMIT 1