This whole conversation has put me to thinking about how the climax could have played out differently. Eli asks to be invited in. She tells Jimmy (or whatever his name is. Is it different in the book?) to release Oskar or pull him up so he can breathe. Jimmy sneers at this little slip of a "girl." She uses controlled force to slap Jimmy so he cartwheels into the pool. She tells Oskar that she can't stay around Blackeberg and protect him. Eli asks Oskar to choose between her and his family. Oskar agrees to flee with her because he wants to be with her and because he sees without a doubt that the bullying will go on, probably with grievous consequences. Oskar goes home as though nothing has happened. He packs a few clothes and his Rubik's cube, leaves a note for his mom that he is running away, and disappears into the night with his beloved.
The main effect would be this. There would be no hue and cry in the newspapers. The police would not be looking for Eli and Oskar. There would be no reason to connect the pool (non)incident with the spate of unexplained deaths. The general public would not be on high alert. Although child protective services would be interested, would Oskar just be a number in an underfunded and overwhelmed system, like in the US? There might not even be the 1982 Swedish equivalent of a milk carton picture of Oskar. The school deals with the issue (arson/or Ávila getting beat up) by meting out the usual severe punishment--Jimmy is banned from coming onto school grounds and the other boys get a stern talking to.
Another effect would be that forum members could leave off debating the probably indefensible and possibly unnecessary deaths of three young people.
However, JAL didn't write it that way. I will join the debate with my take on it. It is surely tragic that Eli murders the cunning, cruel, and increasingly violent bullies, but sometimes tragic events occur when untoward circumstances align. It is tragic that the poor bullies were just in the wrong place at the wrong time--three bullies (well, four), a victimized child,
and his vampire girlfriend. If Eli had not showed up, only one child would have died rather than three. But who's counting.
The takeaway from my scenario? Jimmy comically cartwheeling into the pool after Eli slaps him upside the head.