Personally, I have never been convinced of the supposed link between genius, or even great talent, and bad character. Perhaps I have been unusually fortunate, but the people of real distinction whom I have met, some of the greatest men or women in their fields, have mostly been delightful people into the bargain (though not quite all, but I will not reveal the exceptions). In my experience, it is the moderately talented, those with some talent but enough self-knowledge to wish it were more and worry themselves that it is not, who have a tendency to unpleasantness, for they are disappointed and often bitter that their reach exceeded their grasp.
– Theodore Dalrymple, Farewell Fear
This has been my experience too–with very few exceptions.
He left out one group–those of little or no talent, often the pedants, the bureaucratic “managers” or paper-pushers, supervisors promoted to their level of incompetence, and so forth.
They tend to get in the way at best, and often seem to take a malign pleasure in preventing others from doing valuable work. At the very least, they make doing that work more difficult, and require the waste of time and energy to keep them satisfied, or at least quiet.
I don’t know that this group is as self-aware as the moderately talented described by Dalrymple.