Diddy is facing a stunning lawsuit ahead of his sentencing … the mogul’s long-time stylist Deonte Nash is suing him for sexual battery, human trafficking and more.

According to new court docs — obtained by TMZ — lawyers for Deonte claim Diddy turned his dream of becoming a celebrity stylist into a “nightmare” … one he was “forced to endure nearly every single day” during the roughly 10 years he worked for Diddy.

The docs go on to say … “The horrors Mr. Nash experienced continue to plague him even after his employment ended.”

Deonte’s legal team claims Diddy — through his employment — subjected him to “a decade of sexual and physical assault, sexual and verbal harassment, trafficking, degradation and humiliation, threats to his life and well-being, stalking, control, and psychological manipulation.”

The stylist’s lawyers say Diddy allegedly used his power — and threats of harm — to compel Deonte to do his bidding and keep him under his control.

The docs claim Deonte has allegedly continued to receive threats even after his employment … and he still does not feel safe.

You’ll recall … Deonte testified during Diddy’s criminal trial — and when Diddy’s attorney asked if he was considering a civil lawsuit, he replied, “No, I’m focused on getting out of here.” When asked if he retained counsel to consider suing Diddy, Deonte said he has lawyers “to protect me.”