Besides Disgaea (which is pretty much unrivaled in terms of statistic caps, as Void mentioned), the Valkyrie Profile games have pretty high damage caps. In VP1, it wasn't too hard to do 1,000,000 damage in a single combo with the right setup on Freya, and with VP2 if you release your Einherjar perfectly you can make a single character pretty uber with enough stat-increasing items (a single character doing over 7,000,000 damage in one swipe is pretty neat). This is only really necessary if you are playing on a higher difficulty run and fighting the superbosses of course. The damage cap in VP1 is 99,999,999, but there's no way to achieve that much damage in one attack within the game. I don't honestly know what VP2's cap is, but I don't know why it'd be any greater.

Still, nothing will ever compare to Nippon Ichi's insanity.