Continuity mistake: During the battle between Electro and Spidey, the chip on Electro's head swaps from being on the right side to being on the left. It is specially noticeable when Electro overloads.
Continuity mistake: When Harry and Peter talk by the river they're alone in the wide shot, but with a couple to the right in the close-up angle.
Continuity mistake: In the kitchen with his aunt, Peter drinks from a mug. From the opposite angle the arm is lowered.
Continuity mistake: In the scene where the power is out and two planes are on a collision course with each other, the microphone of one of the air traffic controllers changes from a correct position facing his mouth, to an incorrect position hanging way down and away from his mouth, between shots.
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 ★