19. Star Sapphire
Green Lantern was an unfortunate mess, derailed by unrelatable characters and a misguided imbalance that favoured style over substance with a lavish helping of cold CGI as a side. It took a lot of the character's potential and smushed it inconsiderately into the faces of an audience full of DC fans who wanted and expected a lot more. But despite the problems, there was obviously some confidence that the film might just inspire further films, since the Yellow Lantern Corps arc was set up nicely, and there was even a nod to a possible future appearance of villain Star Sapphire. In the Green Lantern comics, Carol Ferris goes on to gain power similar to Hal Jordan's (albeit with a fetching pink outfit, instead of a green one) and turns all nasty as Star Sapphire, which is referenced in the film by the appearance of the supervillain's symbol on Ferris' helmet early in the film.
Star Sapphire is also very briefly referenced in Man Of Steel - the soldier who proclaims Superman to be "hot" is called Carol Ferris.