Here is my ranking in the reverse:
The hardest and/or most-time consuming (which depends, in part, on the school/teacher/student) are: Calc BC (if taught as a one-year course after pre-calc), Physics C E&M
A small step down to the next level: Physics C Mech, Bio, Chem
A small step down to the next level: Eng Lit, Eng Lang, USH, Spanish Lit
A small step down to the next level: World Hist, Euro Hist, Art Hist, Calc AB, Calc BC (if taught as a one-year class after Calc AB)
A HUGE leap down to the next level: everything else