Harvard University's Math 55: Commonly known as "Math 55," this course is legendary for its extreme difficulty and fast pace.
Massachusetts Institute of Technology (MIT) Course 6.042J: This course, titled "Mathematics for Computer Science," is a core requirement for computer science and engineering students at MIT.
University of Oxford's Bachelor of Medicine and Bachelor of Surgery (MBBS): Oxford's medical program is highly competitive and academically rigorous, requiring students to master complex scientific concepts, clinical skills, and patient care.
Yale Law School's Constitutional Law: Known for its rigorous curriculum and intellectual challenge, Yale Law School's Constitutional Law course is considered one of the toughest law courses in the world.
California Institute of Technology (Caltech) Physics 106abc: Caltech's Physics 106abc, also known as "Advanced General Relativity," is an intensive course that explores Einstein's general theory of relativity and its mathematical foundations.