What is the most reported crime in the Northwest side?
most reported crime refers to max(Count(secondary_description))
SELECT T3.secondary_description FROM Community_Area AS T1 INNER JOIN Crime AS T2 ON T2.community_area_no = T1.community_area_no INNER JOIN IUCR AS T3 ON T3.iucr_no = T2.iucr_no WHERE T1.side = 'Northwest ' GROUP BY T3.secondary_description ORDER BY COUNT(*) DESC LIMIT 1