Which coffee is the strongest?

Hello, I'm curious about which type of coffee is considered the strongest in terms of caffeine content and flavor intensity. Is it espresso, dark roast, or perhaps a certain blend that stands out? I'm interested in knowing the specific characteristics that make a coffee particularly potent, whether it's the roasting process, the bean origin, or a combination of factors. Can you help me understand which coffee is generally regarded as the strongest and why?