What is the #1 hardest major?

I'm curious to know, what do you consider to be the most challenging major of all? Is it a STEM field like physics or engineering, where the complexity of the material and the demands on intellectual rigor are seemingly endless? Or could it be something in the humanities, like philosophy or literature, where the depth of analysis and critical thinking required might be equally daunting? Share your thoughts, I'm eager to hear your take on what makes a major truly difficult.