After an intense Season Six, Leah Messer got into a heated argument with her first ex-husband, Corey Simms, on the upcoming reunion special for MTV's "Teen Mom 2." The fight escalated quickly as the focus turns to Corey's new wife Miranda, and Messer had to resort to using her safe word when Corey tried to bring up Messer's past.

"We got along great the past two years," Messer told Dr. Drew about her co-parenting relationship with Corey.

"What's the problem?" Corey asked.

"You tell me what the problem is," Messer said.

"It's that Miranda gave me a backbone to stand up to your bulls--t Leah, that's exactly what it is because I don't care what you think," Corey finally admitted.

It's the first time they've discussed their issues surrounding Miranda on the show, but in a previous episode Messer had been visibly frustrated with the influence that Miranda has on her relationship with Corey as the parents of their twins, Ali and Aleeah.

"Miranda gave you a backbone?" Leah asked. "Do you want to get started on Miranda? Okay, let's go."

Dr. Drew had to intervene between the former couple before things got worse, but Corey still tries to hit Messer with a hurtful comment.

"If I did half the s--t she's done, I wouldn't see my kids," Corey said, but was interrupted by Messer when she then called out her safe word, "monkey."

"It's the stuff that she doesn't wanna go into, she's agreed not to go into," Dr. Drew explained.

Watch the clip below and be sure to catch part two of the "Teen Mom 2" reunion special airing Wednesday, October 7 at 9/8c on MTV.