The record is probably the Yamanote Line in Tokyo, with about 165,000 passengers per hour at peak. That's effectively a conveyor belt made out of trains; there's a loop in each direction with trains every 2 minutes in each direction during peak periods. Each train carries up to 1600 people, and there are 50 trains on the loops during peak periods.
In Germany and Japan on select few HSR lines trains are operating with a frequency of 2 minutes, and 800 passengers per train.
That’s 24'000 per hour.