What was the largest and most powerful organization of the middle ages?

The church was one of the most powerful organizations throughout the Middle Ages. It played a very significant role in the feudal system (which was the order of class structure used in this time). Churches were being built across the country and, not only were they a way to express your religious beliefs, but they were also a social obligation. The Pope was a very powerful figurehead in that time and people believed that he was God's representation on earth. No one dared to go against God and, therefore, the Pope so this is why the church held great power over the lives of the people in the Middle Ages.