Georg Wilhelm Steller, shipwrecked with Vitus Bering, wrote about the little blue foxes that plagued the crew. It took the men a long time, and a great deal of very nasty effort, to teach the foxes to fear the men. At first, the foxes just jumped right up and nipped at them, without the slightest hint of fear, even to the point of biting one man in the masculine member when the man unzipped the tent to urinate outside it. Noises and other displays had no effect on the foxes. It took actual infliction of physical violence.
If apex babies don’t have a fear response they are less likely to grow into apex predators. What they fear is going to vary, but an animal with no fear response would be suicidal. Still, many animals are likely to be driven by hormonal surges, and the fear response may not save them from self destructive behavior. Just go visit the La Brea tarpits. The enormous amount of predator skeletons found show that all the screams and moans of dying predators and prey don’t stop them from going after the tar baby.