I always see a lot of these forums, but they involve every subject. If you are going to make a hardest AP forum, then you need to distinguish between math/science and the humanities.
Here are the math/science AP's
AP Calc BC, AP Calc AB, AP Stat, AP Computer Science A, AP Bio, AP Chem, AP Physics B, AP Physics C, AP Environmental Science
1) AP Calc BC/AP Physics C
3) AP Bio
4) AP Calc AB
5) AP Computer Science A/AP Physics B
6) AP Stat
7) AP Environmental Science
I have personally only taken AP Calc AB, AP Comp Sci, and AP Stat. However, I have friends that compare their APs. So I know that AP stat and env science are jokes.