I don't know if you already clarified this, but i was looking in a few of the first pages and I found someone that said no boss is impossible. Well, that is semi true. If you ever played FF3, (for the NES) then you would know of the Bahamut fight at the beggining. He is impossible to beat no matter how leveled up you are, but i think its impossible to die to.( He always hits 0 or something and his health always reset every turn.) So the only way to continue the game is to run. So, just saying bosses can be impossible, there would just have to be a way to continue the game. (Like running or making the boss optional.)
Oh ya, and one boss I would have to say was the hardest was the Fate battle in Chrono Cross. I think I wasn't leveled up enough though, but I couldn't get past it. And I can't get past it now either, because my memory card with the save on it got messed up. Oh well.
