Three Spoilers that make this movie great
1. The first grand evil guy gets shot mid-sentence.
Granted, he was given enough time to explain the evil plot, but at least there was no silly "let me transport you somewhere else and give you the chance to fight me before I finally kill you dramatically" stuff. Ramble ramble and just as I was starting to yawn bang down he goes unceremonially.
2. The good guy is shot by a kid.
OK we've seen in City of God and elsewhere that kids shoot people but the way the guy's hope to steer the kid back on track just vanished, and the realisation that, despite all your training and skill, half an inch of well-placed metal and 5 seconds of loss of concentration can destroy you - these are simple and very realistic elements that differentiate this movie from the bulk.
3. The second evil guy and the killer kid get away.
It could have been too easy and unoriginal for the good guy to kill everyone, achieve the perfect catharsis, and then reach his limits and die. Yet here he fails midway. Again a dose of realism that does not diminish in our minds his tragic-hero status.
Notice also their expressions after their victory - not celebratory but rather regretful; perhaps some self-awareness settling in, and implicitly some hope for potential redress.
Also loved the gunfight scene, very realistic with timely recharging, shifting positions while pointing the gun, committing around corners and obstacles, and missing more than hitting the targets.
Refreshing movie with great political and social commentary.