>>212788103A lot of people are so focused on what they think Superman should be that they ignore what the neck-snapping scene was actually supposed to mean. The entire movie was set up telling how this alien is rejected at every moment of his life and feels like he doesn't belong, no matter how hard he tries to help people. Then, when he actually finds his own people, he is forced to choose between them or the humans, who have done nothing but push him around. Miraculously, he chooses to protect the humans, but at the cost of the Kryptonians' lives. With all the Kryptonians sucked to the Phantom Zone, Zodd is literally the last one of his kind, and yet again, Superman chooses to protect the humans.
The neck-snapping is jarring and it's easy for us to judge Kal based on our preconceptions of what Superman is supposed to be. But if you just take the scene at face value, solely in the context of the movie, you can see why this scene was tragic. Superman screaming, "DON'T DO THIS! STOP! STOP!!" is not a forceful command. He's pleading with Zodd to stop because the last thing Kal-el wants is to kill the only other Kryptonian. People criticize the scream at the end too for being over-dramatic, but if you look at it this way, that scream makes perfect sense. He had to kill the last of his kind for people who never loved him all because of what, morality? That's a tough pill to swallow even for someone who is bulletproof and can fly.