 Stallone mostly only found gradual work as an extra or side character in films with a sizeable budget until he achieved his greatest critical and commercial success as an actor, starting in 1976 with his self-created role as the boxer Rocky Balboa, in the first film of the successful "Rocky" series (1976–2018).In the films, Rocky is portrayed as an underdog fighter that does battle with numerous brutal opponents, and wins the world heavyweight championship twice.The last two entries in the series are "Creed" and "Creed II", that serve as spin-off films focusing on Adonis "Donnie" Creed, the son of the ill-fated boxer Apollo Creed, to whom the long retired Rocky is a mentor.