Have never hunted them but know some who do, including a trapper.
wont "debate" or vote whether X is a whole lot smarter than Y. Am sure both/all are.
My vote by far goes to the Timber Wolf
More than smart, more than wily or elusive. Try hunting something with all those qualities in 6 feet of snow, when it's -40 before windchill. Try to stay still, and have to be wary of touching gun metal.
Bears are are super smart and wary to. Doubt they'll get many votes because only a few still hunt them.There's more than just that in determing the hardest, or which is the most challenging. It's kind of like asking which taste better. Roast beef or roast beef and gravy.