Sean “Diddy” Combs’ ex-girlfriend, Cassie Ventura, began what could be a days-long testimony in Combs’ sex trafficking trial Tuesday, alleging on the witness stand Combs had subjected her to physical abuse and coerced her to participate in “freak off” sex performances. (Here is a complete list of the allegations against Combs).

Prosecutors allege that Combs, a three-time Grammy winner, used his fame and fortune to create a deviant empire of exploitation, coercing women into abusive sex parties while silencing victims through...