What is the hardest class you have ever taken?

[soliloquy]

Don't know if this counts since its a Military Class:
Reactor Principles at Naval Nuclear Power School.
Basically an insane class that covers such topics as:
Reactor Physics, Nuclear Physics, and reactor dynamics.

For most in the program this is the class that breaks them and causes a failure. When I went through the program this was the class that caused the 75% attrition rate.

Yes it counts. I took Persian Farsi at DLI. I thought that was hard. Those classes sound impossible. LOL