I'm halfway through an IT degree and I find the programming units the most study time intensive. Ethics and the other non-technical units have been criminally easy, especially business ones, but learning fundamental programming languages from scratch took the most effort. I did understand them quite easily though and just had to put the standard work in.
The only subject that really crippled me was Statistical Analysis. I had to re-read and try activity-after-activity to understand concepts. I was never a math guy in school, but knowing how to apply the right statistical formula to a set of data was a very special fucking nightmare. By the time I got it, it seemed to reset from my brain within hours. I had to basically reabsorb the whole semester before my exam because my brain hated it all so much.
I only just passed that unit in what is otherwise a respectable GPA.
What subjects fucked you over in your course?