Tolkien himself declared Sam is the actual main hero of the story, as Sam grows stronger the closer they get to Mordor and Sam is strong and courageous in situations where Frodo fails (understandably) with his own will, which is undermined by Sauron e.g. he storms the Tower/Castle of Cirith Ungol, kills Kankra even though Frodo had forsaken him cause he was blinded.