What is a major difference between the Roman Catholic Church and the Eastern Orthodox Church?

The major difference between the Roman Catholic Church and the Eastern Orthodox Church is that the Roman Catholic Church believes the pope is impeccable in affairs relating to the doctrine while the Eastern Orthodox Church discard the papal primacy notion and considers the patriarch to have human nature and capable of being wrong.

Explanation:

Along with the Eastern Orthodox Church, the Protestants churches also have discarded the belief of papal primacy

The other differences are;

1) That the Roman Catholic Church believes that Mary was given birth to without man's original sin, while the Eastern Orthodox Church believed that Mar was purged of the original sin

2) The filioque clause