George tells the Quakers that he and Jim are “as brave as death and despair.” What do you think he means?

Despair means seperation or lossing all hope that is to stop having hope that the situation will change for improve. As Charlie Chaplin said"Despair is a narcotic. It lulls the mind into indifference" and death is immortal truth of everyone's life. These two(death and despair) make a strong sensation and force from which one could not have any other option left other than to surrender to them(death and despair).

Here,George tells the Quakers that when He and Jim are together they are as brave as death and despair which means having no fear of anything or being out of bounds of worldly affairs of life that is death and depair,he also mean that togetherly they enough strong and capable to face any problem of the world and could make it down as death and despair could bent anyone in the world.