Red Sonja was suppose to be a Conan sequel and instead evolved into a vehicle for Bridgette Nielson.
Sandahl Bergman, who played the love interest here ends up playing the evil queen in that movie. They obviously gave Arnold a big check to play second fiddle.
After Conan The Destroyer, Arnold told De Laurentiis he wanted to walk away from the Conan franchise.
De Laurentiis acquiesced, but requested that Arnold do a "cameo" in Red Sonja. It turned out to be a much longer shoot. When the movie finally came out and he saw the movie poster with his name first and his image twice as large as Brigitte Nielsen's, he felt duped.
That's amazing, that would have been controversial in modern times with probably a social media uproar. Kind of like what happened with The Sapphires poster.
i found a fan edit that makes red sonja feel more like conan 3. with a title card, music and over dubbed conan when asked his name, plus mako does an intro and it ends with conan on his throne.