Pac was a volatile and unrepeatable combination of conflicting forces: He had the flair and playful swagger of Big Daddy Kane, the pro-black militancy of “Fight the Power”-era Public Enemy, and the unvarnished roughness of Schoolly D, whose “P.S.K. What Does It Mean?” effectively invented gangsta rap. Pac took nearly everything rap had been up until his arrival and remade it in his image.