That's undefeated PFL star Kayla Harrison's manager, Ali Abdelaziz, making it clear ... the 2x Olympic gold medalist is a better fighter than every other woman on planet Earth.

But ... but, what about Amanda Nunes??

Abdelaziz says Kayla "looks up to Amanda very much" ... but he's confident Harrison could handle the consensus greatest female MMA fighter ever -- and it's a fight he wants to set up.

"Listen, if somebody writes the check for 8 figures, we can make this fight happen tomorrow."

How about Olympic gold medalist and boxing champ turned 1-0 MMA fighter, Claressa Shields?

"It’s kind of disrespectful when people bring Claressa Shields in the same sentence as Kayla," Ali says.

Abdelaziz says Shields is an amazing boxer ... "probably a future Hall of Famer" -- but she'd stand no chance against Kayla in the cage.

"In reality, you know, it’s 187. It’s a murder. You know, it’s a fact. If Kayla fought the boxer, that wouldn’t even make sense. Claressa fighting in MMA, it’s not going to last probably 60 seconds."

Kayla's manager also brought up Ronda Rousey ... Kayla's former roommate and Judo teammate.

"[Kayla's] everything that Ronda Rousey was supposed to be. She’s Ronda Rousey 6.0. You know what I’m saying?" Abdelaziz says.