I was curious how other people define their characters more, by their positive qualities or their flaws? I got to thinking about this the other day and realised that how I handle my characters has changed over the years. I used to focus on the things my character was good at or the things that people would like about them, but I now find the opposite much more interesting. My character in PTA as an example is intelligent and driven, but I find her obliviousness and temper to be more interesting.
Yeah the flaws are more interesting to play around. Having a character whose main deal is to be good at something isn't as interesting to write as one who has to struggle. I tend to always give my characters flaws these days and balance them around them.
Flaws are interesting because they require growth and development. If your character is already ridiculously good at something or has no personality flaws, they quickly become stale to both read and write. That being said, I don't think you should necessarily focus all your attention on a character's flaws. Characters are people and people aren't two-dimensional, so a good character isn't either and should have a healthy mix of strengths and weaknesses otherwise they risk becoming caricatures. Characters with no redeeming traits are just as boring as characters with no detracting factors.