Alexander the Great?
Greatness is a term that can be used in an array of different contexts. Alexander of Macedon has been called "The Great" for many years, even before his early death. However I do not believe the title "great" can be handed out so hastily. The first thing I want to explain about my view is that I do not believe that the degree of a persons "greatness" is in anyway related to the inherent good or evil of their achievements. To be greatly good or evil is still great. People confuse the meaning of the word great, if you look it up you see definitions such as remarkable in magnitude, degree, or effectiveness. The word has many other meanings but no where in the Merriam-Webster did I see anything about "goodness." That said lets look at what Alexander of Macedon achieved in his short life then decide if his achievements were remarkable in magnitude, degree or effectiveness.
In less then a decade the man conquered most of the known world, probably would have conquered the entire known world had his men not told him it was time to go home. His tactics in battle proved undefeatable countless times on countless battlefields. His campaign spread Greek culture and religion throughout the known world. His name has been remembered through centuries while how many others who ruled in Greece have not. To me Alexander of Macedon was indeed "great." His remarkable achievements speak for themselves. Some will argue that Adolph Hitler went about his genocide with remarkable effectiveness, and I say to them Adolph Hitler although as evil as they come was also great, and his name will flow through time as Alexander of Macedon's has.