Lil Twist is having a bad Friday -- not only is he set to be arraigned for allegedly orchestrating a brutal beatdown of Chris Massey ... he's now being sued for it as well.
In the suit, Massey says Twist and four of his friends came into his brother Kyle Massey's apartment last November without permission, and began to punch, beat, kick, push and choke him. Chris also says Twist and his boys used brass knuckles and a screwdriver during the attack.
Chris says he suffered cuts and bruises, and needed stitches over his eye. Perhaps more painful ... in the suit he says Twist and his crew made off with his Rolex.
Justin Bieber's ex-pal has already been criminally charged with six felonies for the incident -- which means he could be looking at significant prison time if convicted.
He'll be arraigned on those charges Friday afternoon.