The two biggest movie franchises of Sylvester Stallone’s career, Rocky and Rambo, were both ruined by the exact same problem. Stallone kickstarted his own movie star career with his Oscar-nominated script for Rocky, the story of underdog boxer Rocky Balboa rising up to take on the champ. After Rocky launched a blockbuster franchise, Stallone was dissatisfied with starring in just one and created a whole new franchise surrounding his First Blood character, grizzled Vietnam War veteran John Rambo. Both franchises have lasted for decades, and they were both ruined by the same problem.

https://screenrant.com/sylvester-stallone-rocky-rambo-franchises-ruin-sequels-bad-same-reason/