*Again, massive spoilers, turn back now if you have not seen this movie*
...how Superman was forced to kill Zod in the end. People have complained, "Superman wouldn't do that! He wouldn't kill Zod." I'm sorry to burst your bubble, but yes, he's done this multiple times fighting Zod. In issue #22 of Superman from 1988, he was forced to execute the General and his underlings by exposing them to Kryptonite (which would be a terrible way to go since it's slow and painful).
Perhaps you're like, "Well, I don't care what any dumb comic says (which would be weird for you to say, since we are talking about a man who can fly, shoot lasers from his eyes, and freeze things by breathing on them, but whatever), the Superman I know, Christopher Reeve, wouldn't have executed Zod like that." Really? Really?! Let's just roll this clip, then we'll talk.
Did you see that? Prior to this clip, Superman activated a device that permanently de-powered Zod and the rest of the Krytonian criminals. They were no longer a threat, he could have easily hauled them off to jail, but what does he do? He crushes Zod's hand and throws him against a wall, watching as he descends into the bottomless pit below. He simply watches as the second one (I'm not good with names) tries to fly, but then just falls to his death. And he does absolutely nothing after Lois punches the third one of a cliff. He has super speed, he could have easily saved all three of them and not even be winded. But no, he just stood there and watched, all while grinning like an idiot (please note that this is not an insult to the late, great Christopher Reeve, but merely an observation of the goofy smile he was wearing while murdering Zod). In comparison, snapping his neck while screaming at the atrocity he was forced to commit is VERY in character with Superman.
While we're here, let's step away from killing Zod and address another issue people seem to have: "Why didn't Superman just go back and talk to the Jor-El simulation to find out how to defeat Zod when he showed up?" I've seen a few people bring this one up, but really, Jor-El wouldn't have known how to stop Zod's ship at first. Remember, it wasn't until he was uploaded into Zod's ship that he found out they retrofitted the Phantom Zone generator into an engine. Only then did he have the knowledge that they use that to send the ship into the Phantom Zone.
Lastly, "Why did Superman let them cause all that destruction? Why wasn't he able to contain it better." I'm beginning to think you and I did not see the same film. I mean really, if you're just one guy (a super guy, yes, but still one guy) going against an army of near-invincible, highly trained soldiers with technology so advanced that it warps the gravity around it, don't you think there would be a lot of collateral damage?
It's okay, though. I'm sure you can probably take comfort in the fact that Batman will inevitably address all of your grievances with Supes in the next movie in a calm and rational manner (by punching him in the face with a piece of Kryptonite).
Till Next Time, Space Monkeys!