Sadako Vs. Kayako: Dawn of Justice
It's the Japanese equivalent of Freddy Vs. Jason, only with a smaller costume budget and way more creepy wells. It tells the now classic story of some teenagers watching a cursed VHS tape, who then meet another teenager who is cursed because she lives in a haunted house. They get the admittedly awesome idea to team up and pit their respective curse ghosts against each other, but it does the complete opposite of work. Instead of destroying each other, the two ghosts join forces to become a fantastical super phantom and just fucking kill everybody.
NBCUniversal Entertainment Japan
"Guys, be real. Is there a nude ghost kid on my neck?"
Unlike Freddy Vs. Jason, where both franchises had become ridiculous parodies of themselves even before they fought each other, Sadako Vs. Kayako is a complete tonal shift from either Ringu or Ju-On. While the original franchises were slow-burn horror films that gradually cranked up the creeps, the Ju-On vs. Ringu film is paced like a meth lab explosion.
They even reduce the amount of time you have left to live after watching the cursed VHS tape -- in the original, you have seven days to spread the curse or else suffer a death that can only be described as "embarrassing." In Sadako Vs. Kayako, you have two. The film is so eager to skip straight to ghost murder that they increased the speed of their curses by 350 percent. The film ends (SPOILER ALERT) with the two ghosts merging, proving that even in the afterlife the free market favors consolidation.