The question was does suffering build character.
I say no for the following:
You can suffer to build a better body, you can suffer to learn skills, and you can go through suffering to get something done or just survive. But your character is something you learned growing up by watching others and defining yourself in your mind. Building character comes from how you were raised and what you take as your ideals. Character is composed of the qualities making up someone's
personality.
If your getting constantly shat on growing up, and have no one to give you a hand or advice. Chances are very good your character traits will consist of poor ones. But if you have someone give you a hand, lend you a shoulder or even show you how to go forward. Then your character could develop to be a better, because you have an example of good character.
Suffering is used by many militaries and agencies of the world. They exhaust you and break you mentally down through group suffering, either to give you concentrated accelerated training or so they can mold you to their standards of being a part of a unit. They do not change your character. If you are a Blue Falcon before you join, you will still be a Blue Falcon afterword. You just will be a Blue Falcon who has learned what is required by the military/agency, and that is what you will do when everyone else is watching.
Mind you, if you survive intact from suffering, what you learn is more about your own character and its limits, rather than actually building on it.