Suggested by Destroyer Raikou is a Pokemon of unbelievable power. He is one of the legendaries after all and while that term may not mean a whole lot with some of the fighters, for the most part you can expect a tough fight out of that. Shiron has power ups of his own but I don’t think he would be fast enough to escape Raikou’s attacks or powerful enough to take him out in time. Ultimately Shiron will go down here. Raikou wins.