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Sean "Diddy" Combs is on a heater, at least when it comes to tackling the mountain of lawsuits he's facing ... and now former "Making The Band" singer Sara Rivers is finding out firsthand what kind of roll he's on.

According to new legal docs, obtained by TMZ, a judge just threw out 20 claims Sara made against Diddy in her lawsuit. They were dismissed with prejudice, meaning they cannot be filed again. Instagram / @realsararivers

Among the claims dismissed ... racketeering, assault and battery, forced labor, sexual harassment and false imprisonment.

The only claim remaining against Diddy is one under the Gender-Motivated Violence Protection Act ... and the judge says he's waiting for a ruling from a higher court to determine whether to dismiss this claim as well.

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