Factual error: Towards the end of the film, Spiderman takes his web and uses it to connect to the different power conduits that Electro blew open, ties them together, and power the city back up. Electricity uses several different wires, and crossing them would cause things to blow up or short out. What should have happened when Gwen threw the switch was another power failure, instead of the city's power being restored.
Factual error: A helpful automated voice from Oscorp informs the robbers that "Plutonium-838 is a radioactive material and is highly explosive." No it's not. It is radioactive obviously, but it is not some volatile explosive. (00:09:10)
Answer: Peter didn't set out to kill Electro, but he has to stop him somehow. Overloading him is pretty much all Peter has to work with in terms of stopping Electro's rampage. He doesn't know what effect it will have on his opponent, but he hopes that it will serve to stop him in his tracks, which it does. Had Peter set out with the specific intention of killing Max, that would indeed have been wildly out of character, but he didn't - he simply did what he had to do to stop him. It's unlikely that Max is actually dead anyway; it's well known that Sony intend to bring the Sinister Six into play in upcoming movies and Electro has been a key member of most incarnations of that team, making it highly likely that he'll be back.
Tailkinker ★