I know, I was answering if he is "unstoppable".
And Franklin in one of those futures has been smashed to death by the Hulk.
Like his mother, we've seen him survive impressive things thanks to his shields (He tanked a Celestial blast and he could talk with Black Bolt) but we've never seen him do things like resurrect himself or have a healing factor. Without consciously using his powers he doesn't appear to have increased durability.
To take a stupid example: If you caught Franklin Richards and Silver Surfer by surprise in their sleep and shot them in the head, the bullet would ricochet off Silver Surfer but kill Franklin.
If you were to face both awake, Franklin Richards would beat you more easily than Silver Surfer.