Well, the thread is entitled, "What is the hardest GYM ever?"
Sooo, shouldn't it be a over-all rating for the puzzle, trainers and the leader?
Oh, and sorry for having kinda mean tone.. I don't mean it, promise. :D
Sooo, for me, I think the hardest gym would be.. Hmm.. I dunno, HAHA. I think Mossdeep City Gym? Or, Snowpoint. (Those ice types can sweep your whole team without a fire type, yes, a fire type only, Candice's Frosslass can KO those fighting Poke's.)
But, I haven't tried playing Gen V games yet.. My DS got broken before I had to try. AAAAAARRRRRGGGGHHHH!! Whyyyyy!?