What makes a good flaw for a character. I know what I want in a character to explain why and how they ended up that way, but some of the time, with certain characters I think I end up going to far. For my sci fi piece, the character Hayabusa is the sole survivor of an ambush by a pirate gang. He was run out of the army for 'psyche' reasons, basically he has seriously bad dreams, often reliving that ambush, or seeing former team mates taunting him about surviving. Is that going to far? With another story, Balance as you know it, Leon and Sheree depend on each other too much, they end up feeling lost without the other around. Is that enough of a flaw for them, or is it too little? I guess what I am saying, is how do to make all of the little details I know make them human beings visible to the reader, without being like a certain washed out 80's rapper/MC (Must stop the hammer time).
I think the best answer is to just observe people around you. Try to see all sides of them, the annoying habits of the people you like, and the vulnerable or sweet moments of those you don't. Watch how people treat one another, and see how that causes them to treat others in turn. Everyone is flawed, and no one is without any redeeming characteristics. Sometimes you need to look very hard to see the non-dominant aspects, but it can be very rewarding to make the effort - especially if you want to write about people and have them seem real.
I'd question the idea that Post-Traumatic Stress Disorder is a "flaw", actually. Likewise depending on someone... those aren't flaws to me. Popular fiction is full of people who have disabilities of some kind (I'm reminded of the Dark Tower, where a man with missing fingers, the boy he's killed, a woman in a wheelchair and an addict go on a quest together). I think of those as characteristics. Macbeth depends heavily on Lady Macbeth, which is a characteristic. His flaw is that he can't say "no" when she suggests he should commit a murder.
True, but the fact is considering what they do, well, mortal peril (Leon and Sheree) is in the job description, if not one of the major points. Hayabusa, PTSD seems right, but don't we all have bad nightmares, as far as these traits go, I need them to seem human, not over the top ie, missing fingers or limbs. These are ordinary people, doing extraordinary things, and I don't want them to come off as a better person than you (the reader), but someone that is just like them, in their own way. As far as showing all of their sides, I try, but some of the time I don't feel it goes far enough...
I think satire would be very helpful in showing the flaws of a character. Ridicule and pick at human flaws that are shown specifically in this character, think of things that lower your faith in humans, that you don't like about humans, things that make them imperfect. Good luck
I usually make flaws by looking at each of the personality traits as a double-sided coin. For example, if your character is good at fashion, knows how to dress, and is good with people, they may revolt at a bad dresser, want to compulsively change them by using back handed comments about their dress (So passive aggressive) and can't study for the life of them because they are too busy socializing. So take the positive traits and turn them around. Same with negative. Japanese dramas are fond of this kind of work... where the characters are peticular and the gut reaction is that they are strange, then over the course of the drama you see what they are good at. For example, this one man is very, very detail oriented, and blunt (In a Jdrama I'm watching). He doesn't interact with people well and the premise is that he's not the type a person would marry. But *because* he's these things he knows a lot, even in vivid and geekish detail (like the width of a spaghetti. So he knows tons of things, making him considerably smart. Since he's people phobic, he is very clean and puts his efforts into being clean. Because he's detail-oriented, he makes a good architect, and an over perfectionist. Because he's blunt and often doesn't know what to say and oblivious, he's learned to enjoy life and his own life. So I like to choose a list of personality traits and turn them to either the other side or for humor to extremes.