What is the hardest black card to get?

I'm often intrigued by the elusive world of elite credit cards, specifically the so-called "black cards." They represent the pinnacle of privilege and exclusivity, but what truly stands out among them? I'm curious to know, in your expert opinion, what is the hardest black card to get? Is it a matter of income thresholds, extensive credit history, or perhaps a combination of both? And how does one even begin to qualify for such a prestigious piece of plastic? The mystery surrounding these cards is almost as captivating as the benefits they offer, so I'm eager to hear your take on what makes a black card truly hard to obtain.