Boxing legend Shane Mosley wagered $1,000,000 on himself, betting he'd BEAT Canelo Alvarez in 2012 ... but unfortunately for Sugar, he not only lost the fight, he netted a NEGATIVE $400K in the process!!
The 50-year-old, former multiple-weight class world champion sat down with Mario Lopez for Triller's "OK Bet" show ... and made the stunning admission.
"They were gonna pay me $600,000 [for the Alvarez fight], but I made a bet for a million dollars that I was gonna beat Canelo, and if I would've won I’d have $6 million," Shane recounts.