Apocalyptic

Films where the Earth (or another planet) is destroyed and either most of or all of humanity (or another species) is killed.

The best way to determine how many died in an apocalyptic scenario is to either use the date a form of media was released or the date(s) given in the media itself and use websites like The Guardian or Population Clock for their exact dates.

If it's an alien planet with confirmed life on it without a population mentioned, use the same methods with Earth's population as a bare minimum.