How many saints have great in their name?

Answer 1

There may be others but here are some of the better known 'greats.'
St. Albert the Great
St. Anthony the Great
St. Basil the Great
St. Gertrude the Great
St. Gregory the Great
St. Leo the Great

There is also St. Athanasius who was given the title of 'the Great' by the Orthodox Church but does not usually have that title in the Catholic Church.

Answer 2

There is no definitive number, as the use of "Great" in a saint's name is not a common naming convention in Christian hagiography. However, notable saints who are referred to as "the Great" include St. Gregory the Great and St. Basil the Great.