if I'm not mistaken this thread is posted under Skyrim Cheats, Hints, and Spoilers.
It's likely been moved since that post was made;
And the enemys I find most of a pain, on my Archer that is, are Hagravens... I know they'd be easier if I melee'd them, but I refuse to, i'm in love with my bow <3
I would say frost trolls, but they've become so easy at my current level.