Avatar was originally planned to be an R-rated film 

Robert Rodriguez, the director of Alita: Battle Angel, has revealed that  2009's Avatar was originally conceived as an R-rated film, and it was later cut down to match the PG-13 audience. 

The Spy Kids director broke the news, during a press interaction for Alita: Battle Angel, which is the feature film version of the graphic novel. While talking about the level of gore in his film, he said, "Alita can be a part of what Jim [Cameron] did on Avatar. Originally, he wrote that to be an R-rated movie. He knew he needed to pull some stuff back so it could be for all audiences, PG-13. And so we certainly kept a good balance I think, especially because with cyborg action you can do a lot more, but I think we kept the right tone."

Alita, which is co-written and co-produced by James Cameron, was initially planned to also be directed by him before Rodriguez took over. The film starring Rosa Salazar, Christoph Waltz, Jennifer Connelly, and Mahershala Ali, is slated to hit the screens on February 14. 
 

Meanwhile, the long-awaited Avatar 2 will be releasing a year later on December 18, 2020.