Slowed regen still heals from lava

Godzilla raised his mighty legs and stepped into the surging river.  Wading through the lava, moving inexorably toward something far ahead, Godzilla exhausted the last of his once-phenomenal strength to take those final few steps.
Hot lava hissed, lapping at the creature’s pitted and grooved hide.  As his flesh was cooked away, Godzilla’s phenomenal metabolism regenerated the damaged tissue--but not instantly, and not nearly as efficient as before.