Complex sentence: Stiffer legislation against prostitution and drugs that followed was the final nail in the coffin for the tongs, marking an end to the darkest period in Chinatown's history had finally come to an end.
Split into simpler sentences: Stiffer legislation against prostitution and drugs that followed was the final nail in the coffin for the tongs. The reign of terror symbolizing the darkest period in Chinatown's history had finally come to an end.