For the modern era, the best general is undoubtedly Gustavus Adolphus Magnus of Sweden - the father of modern warfare. He developed combined arms which was used throughout the rest of the modern era, through to the end of World War I. He devised methods of warfare which allowed his tiny Swedish army to defeat many German states, Poland, the Empire of the Danes, and the Russian Empire. He established the Swedish Empire and made it, in a very short period and with a very small army, the dominant force in Northern and Eastern Europe, and probably the smallest military force to ever achieve such grand power.
Napoleon was heavily influenced by him, as were all the great generals of that era, but Napoleon's greatness came as the result of brute force, he had the largest military force the western world had ever seen, only the likes of Constantine and maybe Diocletian's combined Tetrarchy compared.
Caesar I think was greatest of all time, because he too had a relatively small military force, but was incredibly versatile in his tactics, and smashed every army sent against him. He was unpredictable, he conquered Rome with only ONE legion, he was the father of the Roman Empire, and expanded her territories more greatly than anyone else had. Marc Antony was also great, before he went mad with power in Egypt, described himself as a living God and attempted to conquer all of Asia! After tens of thousands of his soldiers died in the deserts - it left an opening for Octavius to sail south and defeat him.
Bismark, used the divide and conquer technique (Caesar used this a lot to defeat his enemies) in that he established alliances between nations, and then declared war on individual nations including Austria, Denamrk, and France, defeating each of them with ease - and eventually bringing most of the German states under his control in what became the nation of Germany.
Friedrich II was the most successful suicidal military leader in history (although I think many felt that about Caesar and Constantine as well, and both of them were more successful, so maybe most successful suicidal military leader in modern history), a small army of something like 55,000, and he had essentially declared war against earth - the French Empire, the Swedes, Austria, Spain, Russia, Denmark, German states, the Danes - and managed claim a draw against the coalition forces. Although he didn't really gain much, he created a legend of Prussian superiority, which would help lead the Prussians (and by extension the Germans) to become the most powerful nation in the world a hundred years later.
Also, thumbs up to the guy who mentioned Subotai of the Mongols. Certainly one of the very greatest.
I describe myself as a little dose of toxic masculinity.
