Who is the major leader of judaism?

In Judaism the major leader is God. There is no human more sacred than others. however, in the Jewish history the main leaders whom are responsible for the development of Judaism are: Abraham the first follower of God in it's Jewish course, and Moses, the receiver of the Ten Commandments There have been many other important figures in the Jewish history like: Issac, Jacob, Joseph, Aharon... etc. However those 2 could probably fit the description of leaders more than any others.

Answer

Modern Judaism is not centralised and does not have a single leader.