We talked to the 27-year-old undefeated fighter (18-0) at the Grammy Museum in Los Angeles this week ... and asked the Bellator titleholder if he believed he was the best featherweight out of all the MMA promotions.

"Definitely. Hands down. Look at the stats. Look at the finishes. He's great," AJ tells says.

"That's one thing I will say about UFC fans. Them motherf***ers are loyal to the soil. If you ain't UFC, they ain't giving you no props. But, what they gotta understand is the fighters make the organization, not the organization making the fighters."

McKee continued ... "In that case, UFC has made [Volkanovski]. He's done great. He's earned it. He's worked his ass off. But, at the end of the day, 145-pounds, I'm the baddest man walking the planet."

Of course, Alex put on a clinic at UFC 273 Saturday night ... absolutely dominating the "Korean Zombie" (who may be the toughest guy on the roster).

AJ is fighting Patricio "Pitbull" at Bellator 277 Friday night ... in a rematch of a July 2021 fight that McKee won by submission (guillotine).

McKee doesn't know how he'll win ... but damnit, he says he knows he's winning this fight.

But, we also talked to Pitbull, and he doesn't see the fight going down like that.

In fact, Patricio tells us he's winning Friday night ... and will force a third fight with McKee to determine once and for all, who's the best Bellator 145'er.

"[A trilogy] will happen. I will beat [McKee] and we will do a third one," Pitbull says.