Answer: Catholic Church.
Explanation:
For the first time in history, the Catholic Church's authority was seriously questioned by the Reformation. Reformers began to point out irregularities in the church, injustices such as the sale of inductions. Until that moment, no one had shaken the church's authority so seriously, those who would eventually try would end up either at stake or in exile, prosecuted by the Inquisition and the like.
