Legend of Dragoon 2 (4 game discs). "The God Of Destruction"
Impossible to beat if you never got a specific armor "legend casque" back in disk the end of disc 1 for 10,000 Gold. no one has that much unless you but it later, or you find the secret monster to kill for 500 gold a round, but every time you fight that secret monster, it can K.O one of your players, and may run away...
oh, and its also impossible to beat it if you always run from monsters, you need to be near the MAX Level to beat the god.
EDIT: If you play to game through, you may get 20,000 gold total (from disc one to disc 4)to raking up money is really hard... unless you fight special monsters. but there hard to find XD even then, you have to kill that special monster 140 times...