It was said than one of the last Real Madrid vs Barcelona was watched by 600 millions persons. Audience Real Madrid vs Barcelona FC
Is this the largest audience for a sport match or are there F1 or other sport matches which has a larger audience?
According to FIFA, seems that more than 715 million people watched the 2014 World Cup Final source.
So I believe that this events has a large audience than that match
There is a new record, the 2018 world cup final was viewed by 1.12 billion viewers.