Having read both Fallout Equestria (45 chapters, ~600k words) and a spin-off by another author called Fallout Equestria: Project Horizons (77 chapters, ~1.7mil words), it's not really focused on gore. There are certainly some gory scenes in it, but mostly it's just regular old Fallout fanfiction adapted to fit the MLP universe. If there is gore-fetish fanfiction, it certainly isn't popular enough that I ever heard about it, and certainly not as long as 100 chapters :/
Having read both Fallout Equestria (45 chapters, ~600k words) and a spin-off by another author called Fallout Equestria: Project Horizons (77 chapters, ~1.7mil words), it's not really focused on gore. There are certainly some gory scenes in it, but mostly it's just regular old Fallout fanfiction adapted to fit the MLP universe. If there is gore-fetish fanfiction, it certainly isn't popular enough that I ever heard about it, and certainly not as long as 100 chapters :/