Could be based on the comics, but I think DC has been more willing to off major characters in their movies aside from the heroes.
Nolan Trilogy killed almost all the villains sans Joker and Scarecrow. Killed off Rachel. You could say wimped out with Gordon and Bruce/Batman's death.
Man of Steel REALLY killed Zod. Killed off Kal-El's parents and homeworld. And while a silly scene killed off John Kent as well. Killed the dude from the military and the scientist and seemingly Faora.
I mean who knows they could all come back in the next movie, but it never feels like nothing isn't at stakes because people do actually end up dying.
I think killing Rachel was the only legit surprise here. Personally I expect the villains to die rather than survive, and killing off Superman's parents isn't any more ballsy than killing Uncle Ben; it's a part of the origin story, there's no tension about whether it'll happen because of course it'll happen.