Did the two sides anathematize each other in the East–West Schism of 1054? In the East–West Schism, did the two sides anathematize each other, stop considering each other brothers in Christ and members of the Body of Christ?
Strictly speaking, no.  There were mutual excommunications, but they were only intended to apply to the specific individuals involved: Leo IX excommunicated Patriarch Michael by, famously, sending a delegation that laid the bull of excommunication upon the altar of the Hagia Sophia shortly before the celebration of Divine Liturgy, while Michael in return excommunicated and anathematized the legates themselves but not all of the church of Rome.