Well Zebra and Sani definitely have a basis to quantify continent level (Zebra at least in potency). He one shot the Mount Turtle that tanked a blast larger than some of our real world continents and it suffered no damage. Mitsutoshi also confirmed Zebra in the current arc of being capable of leveling cooking island which is about the size of the country of Israel. Not continent level but it was never said that Zebra was only capable of that level and coupled with the Mount Turtle feat, it's not a stretch to say he is continent level. He is country level at least in destructive scope and at least continent level in potency. Sani possesses the Satan hair, which doesn't so much level, but eats everything and it has apparently a multi-planet potential. In area of effect, Sani's destruction should be well above continent level just not in the sense of leveling. More like a Senbonzakura type of attack. Toriko and especially Coco may need to prove themselves a bit more and Coco may not get there given he is more extremely lethal not overwhelmingly destructive like the 3 other Kings. But Toriko has a bit of clout. He probably can't destroy a continent or large country in just one technique, but he can spam multi square kilometer attacks all day and they tend to be exceedingly potent, moreso than any of the other Kings except maybe Zebra's Beat Punch.