The biggest shock of 'Batman v Superman' was the ending, which saw Superman give his life to protect the world from the threat of Doomsday. It doesn't quite mirror his demise at the creature's hands in the comics, but serves as a nice parallel to his killing of Zod at Man of Steel's conclusion. Then he had no choice but to take a life, and here he had no choice but to give his own, both for the same purpose of saving others. And obviously this wasn't a move that was made lightly, and Snyder revealed to Collider that he had some help in figuring out if it was the right move; help he got from exec-producer Christopher Nolan...
"It was pretty early, and [Christopher] Nolan and I had long conversation about it, a really great, sort of philosophical conversation about it. He was really cool because he played an amazing devil’s advocate about why not to do it, and then in the end was like, ‘No you’re right, it’s better to do it.'"
Snyder continues...
"We had a version that we talked about where [Superman] just—this isn’t it, but where he got frozen and shot into space or something, so he’s kinda gone. Because one of the big things I wanted to make sure of was that as we went into 'Justice League,' Bruce Wayne was the one who was gathering the Justice League. I thought it was really important to have Bruce Wayne be the samurai who goes and finds the other samurai, that to me was important. And with Superman around it’s kinda hard, because Superman’s Superman so it’s kinda hard for Bruce to be like, ‘Yeah I wanna put a Justice League together’. It’s like, ‘Okay, but maybe Superman should be doing that. You’re just a guy. You’re a cool guy, don’t get me wrong, but you’re just a guy.’ "
There's that Seven Samurai reference again that Snyder loves. Obviously, Superman's not gone forever. He didn't stay gone for long in the comics, and the film basically ends suggesting he will in fact return. So why kill him at all if we know he'll be back, probably in time for Justice League? Snyder tells EW that it's about making the team vulnerable...
“I also I felt like, without Superman, there is definitely a vulnerability to the team that they’re gonna need to figure something out, you know? Superman does represent the powerful. He’s the Michael Jordan of heroes, he’s gonna score.”
It's also about proving that Superman isn't as invulnerable as he seems, even if he can be revived.
“He comes very close to death in space and the reason why we did that is because I wanted to show — and keep the idea in the viewer’s mind – that he can come pretty close to death and the sun can revive him, or he can be revived. I think something more is gonna need to be done....“I felt like there’s a mythological journey for Superman. There’s the birth, death, and resurrection thing. And when you bring him back, who knows what he is when he comes back.”
Maybe Nolan was the one who suggested such an Inception-like final scene?