By this I mean the overstimulation of the senses that happens while you are there.
My answer is probably Old Delhi. From the sheer population density, the near-constant honking, the utter chaos on the streets, the panoply of religions and ethnicities, the myriad scents and colours that pass you by as you travel down the narrow lanes, and not least the choking air pollution, it is certain to keep you on edge, not necessarily in a bad way.
Are there other cities that come close to, or even surpass, this?
Currently in Tokyo and it’s too much for me
The size of the metropolis, the number of people, or something else?
For me personally Tokyo is fucking magical but I also grew up in a town of less than 20,000 residents in Ohio.