VIII for the simple fact it is easy to break with little effort. Even FFII requires you to put in the time to grind the levels but things like Mid-Magic Refine, refining items you get by the boatload for magic and just the abusiveness of Limit Breaks and Summons in this game makes it the easiest. You lean on the gameplay and it breaks whereas other games either require some grinding, some outside knowledge or exploitations, or were just designed easy in the first place.