Napoleon without question. He had almost won. He just needed to make an organic effort to win the loyalty of European nationalists, wiping out the old states in Germany and Italy totally, including Austria and Prussia, and rebuilding them with Low Countries and Denmark as unitary states in imperial real union with France (instead of the OTL vassal patchwork mess), with Poland and Hungary as independent vassals, make himself the explicit heir to the Romans and Charlemagne and take care that loyal middle classes make up most of the administration outside France. Win Sweden to your side for good by giving them support to annex Norway and keep Finland. Full control of this Empire's borders would have made internal enforcement of the ConSys pretty airtight, and Britain was not going to fare well by trading with Russia alone in Europe. The ConSys was hitting them pretty bad in 1811-12.
He also needed to deal with Russia with a more intelligent strategy adequate to his usual standards. If the Tsar wants a rematch, instead of invading the frozen endless steppes on a wild goose chase, take a defensive stance in Eastern Europe, close to your logistic bases in Poland and Hungary, and smash Russian army after Russian army with your strategic genius until Russia is exhausted and its nobilty officer corps bled white. After Russia is done with, use your undivided might to crush the Spanish insurgents and annex Iberia to the Empire, chasing Wellington in the sea with tail between his legs.
European nationalism was in its formative stage during Napoleon's time, and it would be quite easy to remold the loyalties of the middle classes to the ideal of united imperial Europe (and plenty of cultural and political precedents existed in the Romans and Charlemagne). With a prosperous, stable Empire, and Napoleon giving back some liberal reforms, as he planned to do in his late years, European middle classes would flock to imperial administration, making imperial rule unshakable after the defeat of Russia. Britain would be powerless to challenge this continental hegemony, which in due time can easily outbuild its naval supremacy.
In comparison, Charles V was orders of degree less close to success than Napoleon. He did no real effort towards the political unification of Germany and Italy to a degree comparable to Spain, the HRE remained a feudal patchwork mess, and France remained defiant. And he was successful neither in suppressing the Reform neither in taking lead of it and bringing it to its full potential, remolding its Empire's religious allegiance into an Anglican-like Imperial Church (which would have allowed him to unify the HRE). Control of the New World colonies does not balance the equation with Napoleon's achievements and closeness to success.