Astronaut
The astronaut exists within an envelope of profound biological fragility. Without the protective cocoon of spacecraft and spacesuit, an astronaut would perish within approximately fifteen seconds. Bone density diminishes at 1-2% monthly in microgravity, and the cardiovascular system gradually deconditions.
Spongebob
Spongebob's durability defies biological law. He has been flattened, dehydrated, frozen, burned, torn into pieces, yet regenerates each time with no apparent physical or psychological trauma. His durability appears functionally infinite, limited only by the constraints of animation rather than biology.