Justin Bieber -- Lil Twist on Chopping Block After Battery Allegation

Justin Bieber's manager Scooter Braun is sick and tired of Lil Twist bringing Bieber down -- in fact, he wants Bieber to sever ties with the rapper entirely once and for all ... but Bieber is STILL fighting to keep him around.

As we reported, Twist has been accused of battering some girl at Bieber's Calabasas mansion Thursday morning -- but it's only the latest example of Twist's reckless behavior ... a list that includes smoking pot, driving like a lunatic, and getting a DUI.

Bieber has refused to turn his back on Twist once already -- but Scooter has had enough, telling Bieber the battery allegations are the last straw.

We're told Scooter is putting his foot down, insisting Twist is nothing but a parasite sucking Bieber dry -- and the singer needs to drop him like a hot potato stat ... before he does any more damage.

But stupidly, Bieber is still sticking by his buddy -- in fact, we're told he and Scooter had a blowout fight on Thursday when Scooter said Twist had to go.

Which means Twist's days are numbered -- because in a fight between Scooter and Twist, Bieber will almost certainly side with his trusted manager. He'd be dumb not to. Then again, dumb has kinda been Bieber's M.O. recently.