The Great LIVERPOOL FOOTBALL CLUB
That is debatable. Michigan has had the most fans in a stadium in a game, and there are fans growing everyday.
Persepolis is the greatest pro football team.
Liverpool Football Club
Most likely the pittsburgh steelers
It could possibly mean that both the club and fans are united.
Well, Real Madrid is the most widely supported club in South America. However, the South American club with the largest fan base would be Clube de Regatas do Flamengo: Brazil's most popular team with approximately 35 million fans.
PSG by a long distance