In the Oxford English Dictionary, definition II.12.a. of “character” is: “A description, delineation, or detailed report of a person's qualities. Now chiefly historical.” As an example, one R. Lucas wrote: “He undertook to write characters of Pitt and Bonaparte.” The originator of this practice — in some formal sense; surely people have been doing it as long as there have been people — seems to have been Theophrastus. He certainly gives us the term. 

“A character,” in this sense, is what we might call a “character sketch” — a brief summary of a person’s essential nature or … well, character. (There’s not, it occurs to me, a close synonym.) One of the most fascinating features of Hume’s History of England is his “characters,” that is, his summative accounts of the key figures in his narrative, most of them monarchs. Sometimes Hume can do this briefly, and when he is brief he is often fierce, as in this “character” of Richard III: 

The historians who favour Richard (for even this tyrant has met with partisans among the later writers) maintain, that he was well qualified for government, had he legally obtained it; and that he committed no crimes but such as were necessary to procure him possession of the crown: But this is a poor apology, when it is confessed, that he was ready to commit the most horrid crimes, which appeared necessary for that purpose; and it is certain, that all his courage and capacity, qualities in which he really seems not to have been deficient, would never have made compensation to the people for the danger of the precedent, and for the contagious example of vice and murder, exalted upon the throne. 

That’s Richard, done and dusted. But other figures are more complicated. One of the most notable in this regard is his summary judgment of Henry VIII: 

It is difficult to give a just summary of this prince's qualities: He was so different from himself in different parts of his reign, that, as is well remarked by lord Herbert, his history is his best character and description. The absolute, uncontrolled authority which he maintained at home, and the regard which he acquired among foreign nations, are circumstances, which entitle him, in some degree, to the appellation of a great prince; while his tyranny and barbarity exclude him from the character of a good one. He possessed, indeed, great vigour of mind, which qualified him for exercising dominion over men; courage, intrepidity, vigilance, inflexibility: And though these qualities lay not always under the guidance of a regular and solid judgment, they were accompanied with good parts, and an extensive capacity; and every one dreaded a contest with a man, who was known never to yield or to forgive, and who, in every controversy, was determined, either to ruin himself or his antagonist. A catalogue of his vices would comprehend many of the worst qualities incident to human nature: Violence, cruelty, profusion, rapacity, injustice, obstinacy, arrogance, bigotry, presumption, caprice: But neither was he subject to all these vices in the most extreme degree, nor was he, at intervals altogether destitute of virtues: He was sincere, open, gallant, liberal, and capable at least of a temporary friendship and attachment. In this respect he was unfortunate, that the incidents of his reign served to display his faults in their full light: The treatment, which he met with from the court of Rome, provoked him to violence; the danger of a revolt from his superstitious subjects, seemed to require the most extreme severity. But it must, at the same time, be acknowledged, that his situation tended to throw an additional lustre on what was great and magnanimous in his character: The emulation between the emperor and the French king rendered his alliance, notwithstanding his impolitic conduct, of great importance in Europe: The extensive powers of his prerogative, and the submissive, not to say slavish, disposition of his parliaments, made it the more easy for him to assume and maintain that entire dominion, by which his reign is so much distinguished in the English history. 

One of the most Humean elements of this account — and one of the wisest — is his insistence that circumstances conspire to reveal certain aspects of a person’s character, with the implication that in different circumstances the person’s career could have been very different. And since circumstances are always subject to change — “Events, my dear boy, events” — one cannot safely write a person’s character until he or she is dead. 

Among those circumstances is, of course, the very fact of kingship itself. James II, for instance, is someone who could have been admirable if he had not been king: “He had many of those qualities, which form a good citizen: Even some of those, which, had they not been swallowed up in bigotry and arbitrary principles, serve to compose a good sovereign.” (By “bigotry and arbitrary principles,” Hume means, of course, James’s Catholicism.) And: 

In domestic life, his conduct was irreproachable, and is entitled to our approbation. Severe, but open in his enmities, steady in his counsels, diligent in his schemes, brave in his enterprises, faithful, sincere, and honourable in his dealings with all men: Such was the character with which the Duke of York mounted the throne of England. In that high station, his frugality of public money was remarkable, his industry exemplary, his application to naval affairs successful, his encouragement of trade judicious, his jealousy of national honour laudable: What then was wanting to make him an excellent sovereign? A due regard and affection to the religion and constitution of his country. Had he been possessed of this essential quality, even his middling talents, aided by so many virtues, would have rendered his reign honourable and happy. When it was wanting, every excellency, which he possessed, became dangerous and pernicious to his kingdoms. 

If he had remained Duke of York, his vices or shortcomings would have been regrettable but not especially consequential; but when he became King, they ended the dynasty of the Stuarts. I find myself remembering, in this context, a comment Northrop Frye makes in his discussion of tragedy in Anatomy of Criticism: 

Aristotle's hamartia or “flaw,” therefore, is not necessarily wrongdoing, much less moral weakness: it may be simply a matter of being a strong character in an exposed position, like Cordelia. The exposed position is usually the place of leadership, in which a character is exceptional and isolated at the same time, giving us that curious blend of the inevitable and the incongruous which is peculiar to tragedy. 

“Inevitable” because of the circumstance, the position; “incongruous” because one can easily imagine circumstances in which that particular person had been not cursed but blessed, not ruined but flourishing. Hume is exceptionally attentive to this irony of human life.