Beat it on Hard. The final boss on hard was insane. Not really the boss so himself so much as his sludge minions. There are just so many of them and they do constant attacks for big damage WHILE the boss is making to play jump rope. Haha. Anyways, after many deaths, I beat him.
As I've said before, this game is really fun and underrated. If you haven't played it, but enjoy hack n slash games like God of War, it's worth a rent or possibly buy if you can get a used copy really cheap (new is $20, so used even cheaper).