Why Mendelssohn? A Chassidic tradition. Fascinating Footnotes I

It was reported in the name of Rabbi Chaim of Zanz that Mendelssohn was a great Torah scholar and potentially had the power to do tremendous good, but his soul's source was intrinsically evil and therefore he sinned and caused others to sin as well. In fact he was a reincarnation of "Oto ha-Ish" who had visited the world three times: Before the destruction of the Second Temple, as Mendelssohn and as one of the Maskilim of Italy [the writer had forgotten his name. Possibly Samuel David Luzzatto (Shadal)]. To counter Mendelssohn, God had sent the soul of the Chasam Sofer to the world. (She'elot u-Teshuvot Levushei Mordechai, Yoreh De'ah (Tolcsva 1912), Siman 88.)

R. Y. Tassuig, Beit Yisrael ha-Shalem, 4 (Jerusalem 1976), p. 100, cited in the name of his rabbi, Rabbi Shmuel Rosenberg of Hunsdorf.