Marvel has a lot riding on Captain America: Brave New World. Fans loved Sam Wilson, but his shared buddy cop series with Bucky failed to impress. Brave New World will be his proper debut as the new Captain America. He'll rebrand with a new cast of allies and enemies. MCU fans are thrilled to experience Red Hulk and the Leader, but there may be another antagonist in the mix. A new Diamondback may join the MCU in Captain America: Brave New World.