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.
Mikhail Frunze
Frunze died on 31 October 1925. There has been speculation that Stalin or another rival within the party secretly ordered his death, but there is no evidence to support this. However, Frunze was administered a chloroform dose that seven times exceeded the dose normally applied to induce narcosis.