Kourtney Kardashian and Kendall Jenner Go Off on Kim Before Shocking 'KUWTK' Fist Fight: Watch

Kim and Kourtney Kardashian in 'KUWTK'

Kourtney Kardashian and Kendall Jenner are not having it when it comes to Kim.

We finally know the context of that headline-making fist fight between Kim Kardashian West and Kourtney Kardashian on season 18 of Keeping Up With the Kardashians.

In a new clip that dropped on Thursday, the tense argument that led up to 40-year-old Kourtney calling 39-year-old Kim a "c**t" and Kim punching and kicking her in return is revealed. It all starts when Kim and 24-year-old Kendall Jenner have a conversation about work ethic, and Kim implies that she and 35-year-old Khloe Kardashian work harder than Kendall and Kourtney.

"The problem is, if I was on my death bed, I would still show up," Kim tells Kendall. "Mom is so used to me and Kourtney -- eh, Khloe -- going on our death beds."

When Kendall includes herself in the list, Kim savagely points out that Kendall gets anxiety and cancels appearances. Kendall has been open in the past about suffering from anxiety and getting panic attacks.

"Are you f**king kidding me?" Kendall retorts. "Like, I literally will come at you right now. I swear to God. ... I've been sick as f**k, having major panic attacks. I work my f**king a** off when I'm sick or not."

But as Kendall and Kim's conversation gets heated, Kourtney -- who's been sitting with Khloe nearby -- jumps in. Kourtney has been at odds with the rest of her family in recent years about no longer wanting to be on their reality show.

"But you act like I don't do sh**," Kourtney tells Kim. "You have this narrative in your mind. ... I will literally f**k you up if you mention it again. Literally shut the f**k up and don't laugh like that. You look like a freak."

Kourtney explains to KUWTK cameras that she's fed up with Kim constantly saying she has a stronger work ethic than her.

"It's such bulls**t," she says. "We don't all have to do things the same way."

Kourtney and Kim's fight eventually turns physical when Kourtney throws an object at Kim.

"But if I wanted to be a stay-at-home mom, then that's f**king fine, you f**king literal c**t," Kourtney tells her.

As for Kim's side of the story, she explains to KUWTK cameras that their mom, Kris Jenner, is so used to her and Khloe always following through with their commitments, unlike their other siblings. She references their youngest sister, 22-year-old Kylie Jenner, canceling an appearance at Paris Fashion Week in September because she was sick.

ET spoke to Kim, Kourtney and Khloe in November, and the sisters talked about Kourtney's priorities clearly changing.

"I just decided to spend more time as a mom and put more of my energy there," the mother of three said. "But I'm not saying goodbye."

"I think you'll have to see more of it on the new season, season 18," she added.

Kim then pitched a spinoff starring just her and Khloe.

"Like, just, Kim and Khloe take... Calabasas. That'd be amazing," Kim said. "We can live in the condo with all of our kids and see how that goes."

Not surprisingly, Kourtney was clearly not into it at the time -- "Not for me," she said bluntly.

Watch the video below for more: