What are some of the hardest classes at Harvard?

Any war stories? I’d love to hear about some of the more challenging!

One of the hardest classes is Math 55. Math 55 is often regarded as being the hardest undergraduate math class in America. It is a 1 year long course consisting of Math 55a and Math 55b typically taken by freshmen. The course is highly abstract pure math. Interestingly, a very high proportion of the class receive As but this may be a function of the self selection whereby only extremely talented math students take the class. In an average week the class alone can take 20-50 hours. For many the class is the equivalent of a full time job!