So, I think that one of the problems that I have with so many books and movies and television shows these days is that the writers often forget that power should always come with some kind of price tag. More than that, though, that the price should be, both related to the power it accompanies, and somehow similar in scale.
One of the most annoying things I find in vampire literature is when the only downside to becoming a vampire is that you get all whiny. I’ve read a few books like that. The main character bemoans his status and considers himself damned, but has a totally manageable bloodlust, a slight aversion to sunlight, and is completely unaffected by articles of faith.
One of my favorite examples of the cost of power properly associated with the degree of power is in Firefly. You have the Captain, whose skill and resolve are the result of having the joy and hope beaten out of him over the course of a long and miserable war. Zoe, the consummate soldier, is incapable of shedding her attachment to military formality. She MUST obey her captain. She MUST hide her emotions. Then there’s the doctor, who has dedicated himself so fully to his practice that he is barely functional outside of a hospital. He is constantly putting his foot in his mouth, constantly unable to relate, but dammit he’s brilliant.
You can go down the list, and each and every character has a greatness associated with them, that has also cost them in some way. And the most powerful character, River, is also the most flawed, being, depending on how you view her, either completely nuts, or one hundred percent sane. Either way it amounts to the same thing, and makes her as much of a liability is she is an asset.