A rapper with former ties to Big U is happy the Rollin' 60s Neighborhood Crips leader has been locked up on murder and conspiracy charges ... and wants him put UNDER the jail ... she's claiming to be one of his victims!!!

TMZ Hip Hop recently ran into SKG, a former Death Row artist -- whose name stands for "Suge Knight Girl" -- out this week and she's packing a lot of opinions regarding the Big U RICO charges.

SKG tells us Big U was a literal monster to her and the Crenshaw community for years, by allegedly using brute force to extort local businesses.

She also claims Big U beat her in the presence of Nipsey Hussle while she was pregnant!!!

She's been telling the story for years ... Nipsey and his late friend Stephen Jiles "Fatts" Donelson allegedly set her up to be ambushed and beaten by Big U after he was embarrassed by the way he was presented during a meeting with L.A. radio station KDAY.

SKG says she has no sympathy for Big U, but her heart yearns for the family of Rayshawn Williams, the 21-year-old aspiring rapper who federal agents allege Big U murdered in Las Vegas back in 2021.

SKG spoke to Williamson's family and even got backed up by Wack 100 -- another one of Big U's archenemies -- but tells us she feels safer since he's been arrested.

And despite her rocky past with the late Nipsey, SKG wants everyone to be on the lookout for Big U to be implicated in the rap legend's murder.

Big U turned himself in on Tuesday while denying all the internet gossip allegations against his character.