Every story I write is different. Some are hard. Some aren't. 'Chronicle' was tremendously easy. I have a hard time comparing my process on different things, but I will say this: The more you write, the better you get at it. That's one of the few things that's markedly true.
The truth is when you have a movie that was as successful as 'Chronicle' was, it's not as quick of a process. There are a lot more voices coming in and saying 'This is what the sequel should be' because there's a bigger expectation and a bigger fear of failure. And that's really what's going on with 'Chronicle 2.
Superman, when he's fighting you, isn't like Batman. He also isn't like Spider-man, who will bully you and make fun of his villains. Why do you think Spider-man's villains all hate him so much? Maybe because as he breaks their bones he's mocking them! Batman's villains are all insane! Superman, when he goes after someone, is essentially not trying to beat them. He's trying to save them from themselves.
What it comes down to is I don't mind if Superman kills people because he has no reason not to kill people. I know that one of the tenets of the character is that he doesn't, but the reason that he doesn't is because having that much power makes you responsible for weaker people.