Diabolically Devious Doctors: Karl Hellfern... 1 and 2

Doctor Karl Hellfern, on each world on which he was born he was an expert in his scientific endeavors. Regrettably, he turned to crime as a means to achieve his dispicable ends. On Earth-One, he devised a "dust of death" with which he attempted to blackmail Gotham City. On Earth-Two, his counterpart developed a lethal pollen extract to do much the same thing. Both madmen were defeated by the Batmen, even after a second encounter with the Darknight Detectives. Their potential was lost as a result of their vanity and villany.