That epic brawl between the siblings left fans shocked when it was shown on Keeping Up With The Kardashians.
But now, some eagle-eyed viewers have noticed evidence that proves just how vicious it was.
Kim and Kourney were screaming at each other and slapping each other after an argument turned physical.
Sister Khloe desperately tried to get between them and pull them apart, but they continued to fight, spilling from the room they were in to the corridor.
At one point, Kourtney slapped Kim so hard across the face that she crashed into the wall, leaving a smudge of make up behind.
One fan tweeted: “Can we acknowledge the fact that Kourtney popped Kim so good that her skin makeup can off”
Another commented: “Oooo so kourtney actually won this one…”
And one wrote: “Kourtney got her good LMAOOO”
Kim admitted that the fight was so bad they had to abandon filming for a week afterwards.
And when momager Kris Jenner saw the footage, she broke down in tears.
Speaking on The Tonight Show Starring Jimmy Fallon by video call, she was asked how things were between her and her sister.
Kim said: “It was pretty intense. I feel like it’s been a lot of built up resentment from Kourtney and her just feeling like she really doesn’t want to film any more, so she’s not the type of person to make a decision and say, ‘Okay guys, I’m not going to film’, but she would come to work with an attitude every day, kind of take it out on everyone from the crew, to us, and wouldn’t really make that decision.
“So we would kind of like, just keep on pushing her to find out what she was so unhappy.”
Jimmy jumped in to say he had never seen a physical fight on the show before.
Kim continued: “No, you haven’t. It’s not really what we do. I mean, when my mom saw that, a clip of that, she cried.”
The mum-of-four added that she and Kourtney are fine now, but that they had to shut down production for a week after the brawl.
She said: “I think everyone was really shook for a minute and was like, this isn’t our type of show, what’s happening?
“We want everyone to be comfortable and safe, but you know, that happens.
“I don’t really ever resort to violence like that, but she scratched me so hard, which you guys didn’t see, I was bleeding!
“You don’t really get to see that detail, but when I looked down at my arm and I saw that she had really scratched me and I felt it on my back, I just went over and you know, slapped her back.
“So it’s not my proudest moment, but we were going through it and she’s made the decision to take time off now and I think she really needs it.
“I think that’ll be so much better for her.”