Diddy is on a roll, legally speaking … because he keeps racking up wins in court … after outfoxing federal prosecutors, he’s now dealing a major blow to one of his sexual assault accusers.

Here’s the deal … a woman named April Lampros sued Diddy last year, claiming he raped her multiple times in the 1990s — but those allegations are no longer part of her lawsuit.

According to new legal docs, obtained by TMZ, the woman’s claims for battery, sexual assault and negligent infliction of emotional distress have been dismissed.

The only claim remaining here is one under the Gender-Motivated Violence Protection Law based on an alleged incident in late 2000 or early 2001 … Lampros says Diddy went back to her apartment after they bumped into each other in NYC and “violently grabbed her and forced himself onto her.” She says she was able to fight Diddy off, and he left.

Diddy’s camp tells us the dismissals “significantly” narrow this particular civil case … but Blackburn says, “It’s a win. The case moves forward and discovery begins.”

As you know … Diddy dodged a bullet last week when he was acquitted on racketeering and sex trafficking charges in his federal criminal trial, with prosecutors taking a monumental loss by only being able to secure convictions on lesser charges involving prostitution.

Diddy’s lawyers tell TMZ … “Mr. Combs’s trial and acquittal on trafficking and RICO charges prove what we have been saying all along: Mr. Combs never sexually assaulted or trafficked anyone.”