The original Mortal Kombat movie did a good job of capturing the vibe of the series, but definitely not the tone. To do that, it would have needed an R rating. You can't really show what Mortal Kombat is all about with a PG-13 rating. While the first two films took that route, the brand-new installment is going all-out with an R. This was confirmed by the movie's screenwriter, Greg Russo.
“Since it’s already been stated by other members of the team, I’m gonna put this one to bed. MK WILL be R-Rated and for the first time EVER, FATALITIES will FINALLY be on the big screen (and no I’m not gonna say which ones) You’ll just have to wait for the movie & see!!!”