Question: Rainbow Girl was most recently a part of Action Comics who introduced what major superhero charcater?

Context paragraphs:
Rainbow Girl: Rainbow Girl (Dori Aandraison of the planet Xolnar) is a fictional character and a DC Comics super heroine.  She first appeared in "Adventure Comics" #309 (June 1963) as a rejected Legion of Super-Heroes applicant.  Her second appearance was 25 years later in "Who's Who in the Legion of Super-Heroes" #5 as a socialite.  She did not appear again for nearly 20 years until "Action Comics" #862 as a member of the Legion of Substitute Heroes, an organization of teenage heroes that exists one thousand years in a future universe.

Superman: Superman is a fictional superhero appearing in American comic books published by DC Comics.  The character was created by writer Jerry Siegel and artist Joe Shuster, high school students living in Cleveland, Ohio, in 1933.  They sold Superman to Detective Comics, the future DC Comics, in 1938.  Superman debuted in "Action Comics" #1 (cover-dated June 1938) and subsequently appeared in various radio serials, newspaper strips, television programs, films, and video games.  With this success, Superman helped to create the superhero archetype and establish its primacy within the American comic book.  The character is also referred to by such epithets as the Big Blue Boy Scout, the Man of Steel, the Man of Tomorrow, and the Last Son of Krypton.

Action Comics: Action Comics is an American comic book series that introduced Superman, one of the first major superhero characters as the term is popularly defined.  The publisher was originally known as National Allied Publications, and later as National Comics Publications and as National Periodical Publications, before taking on its current name of DC Comics.  Its original incarnation ran from 1938 to 2011 and stands as one of the longest-running comic books with consecutively numbered issues.  A second volume of "Action Comics" with issue #1 ran from 2011 to 2016.  "Action Comics" returned to its original numbering beginning with issue #957 (Aug. 2016).

Barry Kitson: Barry Kitson is a British comics artist best known as a penciler of major superhero comic books published by Marvel Comics and DC Comics.

Hayfoot Henry: Hayfoot Henry is a fiction DC Comics character who made his debut in "All Funny Comics" #1 in 1943, then moved to "Action Comics", where he had a feature story in issues #78 through #118, with one final appearance in issue #123.  This was in a time when "Action Comics" was an anthology title with multiple feature strips.  Henry's strip was intended as comic relief to balance the more serious-toned other features of the comic book, such as Superman.

American comic book: An American comic book is a thin periodical, typically 32-pages, containing primarily comics content.  While the form originated in 1933, American comic books first gained popularity after the 1938 publication of "Action Comics", which included the debut of the superhero Superman.  This was followed by a superhero boom that lasted until the end of World War II.  After the war, while superheroes were marginalized, the comic book industry rapidly expanded, and genres such as horror, crime, and romance became popular.  The 1950s saw a gradual decline, due to a shift away from print media in the wake of television and the impact of the Comics Code Authority.  The late 1950s and the 1960s saw a superhero revival, and superheroes remain the dominant character archetype in the 21st century.

More Fun Comics: More Fun Comics, originally titled New Fun: The Big Comic Magazine a.k.a. New Fun Comics, was a 1935–1947 American comic book anthology that introduced several major superhero characters and was the first American comic-book series to feature solely original material rather than reprints of newspaper comic strips.  It was also the first publication of the company that would become DC Comics.

Rainbow Girl (disambiguation): Rainbow Girl (Dori Aandraison of the planet Xolnar) is a fictional character and a DC Comics super heroine.

Action Comics 1: "Action Comics" #1 (June 1938) is the first issue of the original run of the comic book series "Action Comics".  It features the first appearance of several comic book heroes—most notably the Jerry Siegel and Joe Shuster creation, Superman.  For this reason it is widely considered both the beginning of the superhero genre and the most valuable comic book of all time.

Xolnar: Xolnar is a fictional planet in the 30th and 31st centuries of the DC Comics Universe .  It is the home world of Rainbow Girl, Dori Aandraison.

Supporting paragraphs: Rainbow Girl Action Comics
Answer: Superman