The Saw franchise revolves around one of the most intriguing fictional serial killers seen on screen, and the story of how John Kramer became Jigsaw is almost as intriguing as the traps he creates. Though he puts his victims through brutal death traps, John Kramer (Tobin Bell) always insists that he never actually killed anyone but rather gave them a choice. In Jigsaw's eyes, his traps are a righteous and noble pursuit, helping ungrateful people fight for their lives and once again appreciate what they have. That twisted philosophy grew out of John's many heartbreaks and tragedies, and the story of how he became Jigsaw is understandably a fascinating one.

https://screenrant.com/saw-movies-jigsaw-john-kramer-origin-explained/