I only have a couple of characters with tragic/really horrible back stories. But to be honest, you kinda have to make the character based around that backstory because it will affect every aspect of their life, be it through fear, bitterness, hatred or other base emotions, jealousy etc. One of my favourite characters (sadly ineligible to be played here, though if custom races were allowed, I'd be on it like a shot XD) was exiled unjustly in the subterranean realms of her race and has grown to hate those who exiled her and everything connected to them, it's formed the backbone of that character's view on life - fatalistic, black, forever the pessimist (or realist, as she calls herself) and fuelled by anger, rage and a desire to revenge herself on everyone responsible for her exile. But then, she's also not completely one-sided. She has a soft side, and when someone she cared about asked her 'What will you do after you'd indulged yourself in your little orgy of bloodshed?', that character did almost like a double-take. What *does* someone do after they've had their revenge? Does it give them inner peace? Or is it nothing more than a hollow victory, like Achilles' killing of Hector in the Iliad? When the motivation disappears, when you do finally hear the last pained gurgles as your scimitar plunges through your hated enemy's neck, what happens now? Is it over? Or is it just the beginning?

Every character is multi-faceted. If you fail to take that into account, or simply fail to understand that, then perhaps it's something you need to work on.

Just my £0.02 on the matter.