NO. 1: The Carl's Jr. DOUBLE SIX DOLLAR BURGER.
2 paties, 3 slices of cheese and all the fixins and coming in at a whopping 1500+ calories (with over 100 grams of fat)! Plus, it's really tasty; the Angus beef paties are really well prepared. Calories well-spent.
RUNNER-UP: The Burger King Quad Stacker
I think a close runner-up has to be the Burger King Quad Stacker with 4 patties, 4 slices of cheese and 8 strips of bacon and it doesn't even pretend to be anything but an orgy of fat and cholesterol as it comes with not a shred of lettuce, tomato or any other veggies to speak of. Problem is, this burger is a bit too tall and not wide enough. Hard to eat, almost need a fork and knife, and for fast food, that's not ideal.