A few vices are sufficient to darken many virtues.

People are judged unevenly, and a small number of bad habits will overshadow a great deal of genuine good. It is unfair in a sense, and it is also how attention works, since the discordant note is what gets remembered. A generous, competent, kind person with a temper tends to be described mainly by the temper.

Rather than adding another virtue, work on subtracting the one thing people would name as your flaw. You probably already know what it is. Removing it does more for how you are received than anything you could add.