Don't call it a comeback, call it a payout -- LL Cool J's coming out swinging for Andy Ruiz Jr., saying if Anthony Joshua wants back the belts, he's gotta pay the guy who took 'em.
We got LL at LAX Friday, and the famous fight fan wasn't just riding the "Pay Ruiz" train ... he was the freakin' conductor! We asked him about the new WBO, WBA, IBF and IBO heavyweight champ demanding $50 MILLION, if the Joshua rematch is held on AJ's turf in the U.K.
LL didn't hesitate, telling us .