I have seen a few threads like this so I've tried to pinpoint exactly what I mean while also being aware that there is still room for the decision to be subjective.
In my mind, I split it into two different types of difficulty: Conceptual difficulty and workload.
Some courses may come naturally to people but, for instance, maths is generally going to be seen as more conceptually difficult than management studies while medicine is going to have a higher volume of work to keep up with.
I am curious what degree you think is the most conceptually difficult. To me, the list start of something like this:
Mathematics
Physics
Engineering
Computer Science
Chemistry
I think I perceive the degrees with high maths content as the hardest but that's just from the course reputations. What do you guys think?