Biggest crowd at a Beatles Concert?
On July 4th 1966 The Beatle played two concerts in the Philippines as part of what would be their final world tour. These took place over a single afternoon and evening at the Rizal Stadium, Manila.
The Beatles were told that 30,000 tickets had been sold for the first gig and 50,000 for the second. To their horror they discovered that these figures did not remotely reflect the numbers packed in to the stadium.

As George puts it in Anthology:
...when we got there it was like the Monterrey Pop Festival. There were about 200,000 people on the site.
In the Philippines The Beatles unwittingly upset the dictator, Ferdinand Marcos, played in a dangerously overcrowded stadium and were literally chased out of the country.
Full story (5 min free read) here