Why did the original Hellboy movies not have a thrid part?

Guillermo Del Toro’s original idea for the third Hellboy film was to be epic in scope involving Hellboy facing the apocalypse and having to become the beast of the apocalypse in order to save the human race. In doing this, he would become a much darker being. Because of the epic scale of the story, it would be a very expensive film to pull off and Del Toro was not able to find funding for from any studios. He also wasn’t able to start thinking about doing it until after 2010 because he was busy with other films he was working on such as The Hobbit.

There was a lot of interest in making the film based on interviews of key participants in the making of the earlier films between 2012 and 2014. As of 2017, however, Del Toro has confirmed that there will not be a third Hellboy from him because of the cost and scale of the story.