Purim
There is a tale in the Hasidic Chabad movement that supposedly Joseph Stalin died as a result of some metaphysical intervention of the seventh Chabad leader, Rabbi Menachem Mendel Schneerson, during the recitation of a discourse at a public Purim Farbrengen. Stalin was suddenly paralyzed on 1 March 1953, which corresponds to Purim 1953, and died 4 days later. Due to Stalin's death, nationwide pogroms against Jews throughout the Soviet Union were averted, as Stalin's infamous doctors' plot was halted.
Georgi Dimitrov
Dimitrov died on 2 July 1949 in the Barvikha sanatorium near Moscow. The rising speculations that he had been poisoned have never been confirmed, although his health seemed to deteriorate quite abruptly. The supporters of the poisoning theory claim that Stalin did not like the "Balkan Federation" idea of Dimitrov and his closeness with Tito. A state consisting of Yugoslavia and Bulgaria would be too large and independent to be controlled by Moscow.