There were many Gedolim, Rabbanim, and Rebbeim who had praised, corresponded with, respected and/or looked up to the Lubavitcher Rebbe (ZaTZaL.)
To state a few, Rabbi Moshe Feinstein, Reb Dovid Feinstein, the Baba Sali, Reb Shlomo Zalman Aurbuch, Reb Elyashiv, Rav Kaduri, Rabbi YB Soloveitchik, Rabbi Lau, Lord Rabbi Jonothan Sacks, amongst many many others. As well, in the Lubavitcher Rebbe’s younger years, The Rogatchover Gaon, Reb Menachem Ziemba, Reb Yechezkel Michelsohn, the Teferes Yosef of Radzin, the Akaidas Yitzchak of Alexander, The Imrei Emes of Ger, Reb Meir Shapiro, Reb Chaim Ozer, Reb Baruch Ber and scores of others highly praised the Lubavitcher Rebbe for his tremendous scholarship piety.
Shame on anyone to say that these Gedolim had anything to do with Avoda Zara or anything Heipach Da’as Torah. Shame on anyone who says that these Gedolim heaped praise on anyone who was C”V Maisis uMaidiach!
(Learn Rambam if you don’t know what those terms mean!)