By what metric? I’d argue the driving factor is their proximity to dirty money. Same with Russian banks. Then other people notice you’re used to looking the other way and you get word-of-mouth network effects. With money launderers.
>>JumpCr+(OP)
I don't know much about HSBC's history with dirty money, but they are well known to be one of the most global banks. Only Citibank and Standard Chartered operate in more countries.