Aaron Carter beat Shaq, but could be in big trouble when he boxes Lamar Odom ... 'cause the ex-NBA star sent his opponent to the canvas in a recent sparring sesh, and TMZ Sports has the vid!!!
As we previously reported, AC and LO are training non-stop for their Celebrity Boxing fight on June 12 in Atlantic City ... proving they're serious as hell about the bout.
We're told Odom has been hittin' the mitts with Barry Young at Decatur Boxing in ATL this week ... and it's obvious Lamar's putting in the work -- he even knocked the guy down at one point!!
Remember, we obtained a vid last week of Carter going HAM in the gym ... working with MMA fighter Jesse Strader.
Now, we'll keep it a buck -- these guys aren't gonna be Tyson Fury overnight ... but it's obvious they've got a passion for kickin' ass, and it looks like they'll be ready to go at it come June.
Both guys have guaranteed a victory ... but only one will come away with the dub.