What is the 1 hardest sport?

What is the most challenging sport out there? Is it boxing, where athletes engage in brutal physical combat, pushing their bodies to the brink of exhaustion and injury? Or perhaps it's football, where players must combine speed, strength, and strategy on a massive scale? Or could it be a sport that's less well-known, like rowing or rock climbing, where the sheer physical demands and mental toughness required are truly daunting? Which sport do you believe stands as the ultimate test of human endurance and skill?