What is the name of the competitor who has won the most medals?
name of the competitor refers to full_name; won the most medals refer to MAX(COUNT(medal_id));
SELECT T1.full_name FROM person AS T1 INNER JOIN games_competitor AS T2 ON T1.id = T2.person_id INNER JOIN competitor_event AS T3 ON T2.id = T3.competitor_id INNER JOIN medal AS T4 ON T3.medal_id = T4.id WHERE T4.id != 4 GROUP BY T1.full_name ORDER BY COUNT(T4.id) DESC LIMIT 1