Hedgehog
Operating on approximately 30 calories daily during active periods, the hedgehog represents a triumph of energy efficiency. During hibernation, this drops to nearly zero metabolic expenditure. A hedgehog's carbon footprint is measured in grams. Their diet consists entirely of local invertebrates, requiring no infrastructure, transportation, or ethical debates about factory farming. They are, energetically speaking, nearly perfect.
Hulk
The Hulk's energy requirements remain scientifically inexplicable. He appears to violate thermodynamic laws routinely, generating massive kinetic energy without proportional caloric intake. However, the secondary environmental costs are catastrophic. Each major Hulk incident creates millions of tonnes of debris, displaces thousands of residents, and requires reconstruction budgets exceeding some nations' GDP. The Hulk is not merely unsustainable; he is an economic disaster with anger issues.
VERDICT
If sustainability measures long-term viability without environmental degradation, the hedgehog wins by every conceivable metric. The species has persisted for 15 million years without rendering any ecosystem uninhabitable. The Hulk struggles to visit a city without its insurance premiums doubling. Efficiency triumphs over raw power.