Adrien Broner Will 'Get Whacked' If He Doesn't Grow Up, Says Boxing Legend Ray Mancini

Adrien Broner is ruining his life right now, and it ain't gonna end well unless he gets it together FAST -- so says legendary boxer Ray "Boom Boom" Mancini.

We got the Hall of Famer outside Friars Club in NYC ... and he didn't sugarcoat what's gonna happen to A.B. if the boxing star keeps becoming unhinged.

"That's how you get whacked," Mancini told TMZ Sports. "People take you out for a lot less."

Ray, of course, is referring to Broner's violent Vegas rampage ... where he pushed a woman and KO'd a dude on the strip.

Mancini says Broner's boy, Floyd Mayweather, will try to help him anyway -- if he hasn't already -- but told us Broner's "a grown a** man" that needs to account for his own actions.