Lady Macbeth of the Mtsensk District
It is hard to know why Stalin decided he did not like the opera.  It may have been because the police are made to look silly.  It may have been because it showed people being sent to Siberia.  Maybe it was because Katerina sings a lot of beautiful music, while the other characters have music which often made them look stupid and grotesque.  He may have thought that Shostakovich was being critical of the leaders of the Soviet Union.