My kid would say, as far as the ones he took, with his score:
Most Difficult: AP Physics C E&M(3), AP Lit (5)
Hard: AP Physics C Mech(4), AP Calc BC(5), AP Chem(5), AP Bio (4)
Medium: APUSH(4), Macro/Micro Econ(4,3, self-study), Eng Lang (5)
Easy: Stats(5), Psychology (5), US Govt (4)