Johanna Shmidt was a Nazi leader and scientist. She rose through the ranks to become the leader of Hydra during the Second World War. She was powered by an early and unstable version of the Super-Soldier Serum, and adopted the identity of Red Skull.
Under the Nazi cause, she began to develop multiple advanced creations, the primary focus of weapons research based on Norse mythology, after having acquired the Tesseract.
Since then, she has battled Captain America and her fellow heroes for years, without ever achieving her goals of global domination.
When Captain America and Becky Barnes stormed Shmidt's base, Shmidt and Zola eventually fled once the two made their way upward. Despite Zola wanting to leave immediately, Skull and Cap confronted each other head-on.
Eventually, the power of the Tesseract consumed her, causing her to vanish in a confrontation with Captain America.