Man-Bat

Man-Bat is a DC Comics supervillain/antihero created by writer Dennis O'Neil and artist Neal Adams. He first appeared in Detective Comics #400 (June 1970) as an enemy of the superhero Batman. Kirk Langstrom was a zoologist who tried to give humans a bat's acute sonar sense. He managed to develop an extract that could supposedly do this, but upon testing it on himself, he transformed into an anthropomorphic, feral, half-bat hybrid, lacking sentience and acting purely on instinct. Batman managed to reverse the effects, but Langstrom would return as Man-Bat time and time again, albeit not necessarily as a villain, as Langstrom would sometimes retain enough sanity to use his powers for good.