WitBeyondMeasureisHoid

I can't help but notice that nobody mentioned Wit... He is not a Herald, but he is a more powerful entity than the other radiants, with his other forms of investiture and world hopping. He may not have shown us very strong powers with stormlight, but he has shown signs of using other types of investiture on Roshar. Granted, if you meant most powerful with stormlight, it's likely not him, but he deserves to be on the list, at least.