I think it was Goethe who said of Napoleon that he was as intelligent as a man can be without wisdom, and as great as a man can be without virtue. It seems easy enough to conceive of a person who is highly intelligent but not wise. But, is it possible for a person to be great without being virtuous? Goethe seemed to think so.
I suspect others would disagree. In the western tradition I think those others would, for the most part, be ancient and possibly medieval philosophers. One can almost hear them debating what it is that makes someone truly great, and it's extremely probable that virtue would be a significant attribute of the great, if not the only "great" characteristic, at the end of what I think would have been a very dull day. In the eastern tradition, it seems apparent that Buddha, Lao Tzu, Confucious and other wise men would, at the least, say it is not great to masterfully practice the art of war over the length and breadth of a continent for some 20 years.
There are many, though, who consider such as Napoleon to be great. Although I would hesitate to compare him to Hitler, Heidegger, who worshiped the Fuhrer, is an example of a philosopher who rejoiced in such men of action. Not all were as thoughtful as Pompey, who named himself magnus, thereby saving others the trouble. But there is of course Alexander, and he has had his share of admirers, including Mary Renault, who wrote delightful books about him and his time but accorded him a kind of semi-divine status, which seems to take admiration a bit too far. And there is Caesar, and others.
Teddy Roosevelt used to to speak of the man in the arena as being the only truly great man. One wonders just what arena he was referring to; I don't think huge sports arenas existed during his heyday, or that sports figures had wide popularity. One only hopes he was not referring to the Roman arena.
We speak also of great artists, great writers, great musicians, but in their cases I think we are reserving the adjective "great" to their works, possibly because that is the means by which they are measured. What, though, about great people? What, so to speak, is so great about them?
We humans have a bad habit. For some reason, we seem to feel the need to define things which do not admit of clear definition. We tend to take that need to extremes. We must know what is truly great, or good, for example. We think that there is some ultimate, usually singular, definition to be arrived at; worse yet, we feel we have to determine what it is that is truly great, or good. Once we know that, then we will know how to distinguish the great and the good, in all cases. Better yet, we will be able to become great and good. Even better, we will then be able to tell other people what is great and good; and if we're very fortunate, we'll be able to make them do what we think is good, and what is needed to make them (and us) great.
It is a foolish conceit, I think. Greatness can consist of many characteristics and abilities, and they need not all be present in order to make someone "great." There are things we justly admire in others. Just what will be admirable, though, may vary with the time and the circumstances. Not all great people will be models of what the ancients believed to be virtue. The stoic wise man may well be considered great, but except perhaps as a teacher or model, will not have a great impact on society (too many things will be "indifferent" to such a sage). "Great" is a flexible word, used to refer to the remarkable, the extraordinary and other things. The effort to establish what is truly great, or who is truly great, is an artificial exercise, just as the effort to establish what is truly good, or really true, or really real is artificial in the sense that it can have no practical application in our lives. We don't live through the application of absolutes.