Moshe Schneersohn
Scholar David Assaf uncovered evidence that Rabbi Moshe Schneersohn (or Zalmanovitch or Shneuri), the youngest son of the founder of Chabad, the Alter Rebbe, had befriended an artillery officer. The officer then got Schneersohn drunk at a party and convinced him to convert to Christianity. Assaf also uncovered evidence that there had been a campaign by Chabad followers to erase this fact from the history books. Schneersohn had been a Rabbi in the Belorussian town of Ula. According to Chabad accounts, including the history of the Chabad movement written by the sixth Rebbe, "Rebbe Moshe" was forced to flee and spend the rest of his life in hiding after winning a disputation with the local priest (similar to Nachmanides's forced move after winning the Disputation of Barcelona). Chabad accounts state that he was buried in an unmarked grave in Radomyshl, Ukraine.
Documents found by historian Shaul Stampfer document Schneersohn's conversion to Christianity. The original documents are located in the national historical archives in Minsk. These include a letter in to the local priest in which he states his intent to convert, his baptismal certificate, which was dated July 4, 1820. The documents also show that after his conversion he worked for the Tzar to assist in the conversion of other Jews. In the letter in which he stated his intention to convert he wrote that the Jews had tried to prevent him from doing so by watching him constantly, beating him and threatening him. He wrote: "I have remained steadfast in my desire to take upon myself the true faith of Jesus Christ, to which the holy books and all the prophets testify." After conversion he changed his name to Leon Yoleivitch. He returned to visit Lubavitchi, where his brother was the Rabbi, but fled, ultimately dying in a mental institution in St. Petersburg.
Read more about this topic: Chabad-Lubavitch Related Controversies