Superheroes and body horror.

When Superheroes gain their abilities a lot of the time the underlying fear of their changes isn't always shown and I think that can take away from certain stories. When their powers are caused by an accident why are they not more afraid about the possibility of their mutations further progressing and turning them into a monster or even killing them? I think the canceled Fantastic 4 movie from the 90s did this really well believe it or not; everyone is horrified of their new abilities and Ben who hasn't transformed yet is very concerned for his friends.