Here’s another angle of character design to consider:
What’s your character — especially your protagonist — afraid of?
Do you know? Have you ever thought about it?
Deep down inside, in the secret places of this character’s heart, there has to be something he or she fears. Something he dreads. Something she’s denied or evaded for a long time. Exactly what does your protagonist live with, day in and day out? Maybe that secret fear has been locked away for years. But it’s always in there, waiting for a chance to come out. It can serve you twofold:
1) By giving your character extra dimension. How has this fear or lack shaped the individual as a person? Maybe she’s overcompensated in some way, or learned skills that she would never have otherwise sought. Perhaps it’s warped him, festering away day after day, year after year.
2) By setting up for the story climax. What your character fears speaks directly to that individual’s inner arc of change.
When you start writing the story climax, the time of denial and evasion is over. The antagonist is going to possibly find out about this fear and exploit it, or the protagonist is going to have to confront that old, inner problem and deal with it in order to survive the climax.