So you've decided to make a Conan movie. This is a very good idea, as he's an iconic character with a strong cultural acceptance, a catalog of successful material to draw from, and a good record for translation into visual media.
You've also decided to make it a hard R rating, which is excellent, too. Conan without bloody fighting and bejeweled half-naked women lounging on silks isn't Conan, and trying to sell more tickets by making him all-ages misses the point.
Regardless, your film will fail unless you commit to at least two more principles:
1 - You're telling a Conan story, not the Conan story. This is a character who became part of our cultural vocabulary through novellas serialized in monthly pulps, and cemented his importance in monthly comic books. The formats that have worked for him are ones that implicitly lead the audience to feel like they're seeing one adventure in a lifetime of adventures. It's tempting, when moving the character to film, to try to write a new story that will show us his arc from childhood to adulthood and the resolution of his lifelong quest yadda-yadda-- Resist this temptation. There are established Conan stories that have been successful on their own, and have been repeatedly and successfully translated to visual in comics. Use one of those and don't look back.
2 - Conan is not a culture-hero because he's really good at stabbing people. One of the strongest themes of Robert E. Howard's original stories is the juxtaposition of the free-willed barbarian who goes where he will and refuses to be hemmed in by the will of others, making his own way through his own strength, with the people of the cities who have succumbed to bureaucracy and order, becoming weak and corrupt in their narrow lives of dominance and being dominated. The philosophy of Conan goes beyond libertarianism and arguably beyond anarchism; it's actively anti-civilization and anti-order. It's not a coincidence that the original stories caught the public imagination during the exact same years when FDR was pushing through the New Deal. Your writer and director don't need to share Conan's philosophy any more than the director of a thriller needs to be a serial killer to properly present the antagonist. But Conan has deep cultural appeal because he expresses that part of most humans, regardless of their place on any political spectrum, that chafes at being told how to live. If you're going to tell a story about a superhuman warrior fighting an insane necromancer who lives in an isolated fortress, and your only nod to the theme of the barbarian's wild spirit against the creeping control of civilization is a starkly disconnected line by a co star at the hour-fifteen mark, you are not telling a Conan story.