Which villains were part of Batman's early rogues' gallery?

Batman’s early rogues' gallery featured a variety of antagonists who emerged during the character's Golden Age. The first issue of the Batman comic (1940) introduced two of his most iconic villains: the Joker and Catwoman, who was initially referred to as "the Cat".1

Other notable early adversaries included:

• Professor Hugo Strange: A mad scientist who terrorized Gotham City with poisonous gas and mutated monsters.2
• The Scarecrow, Penguin, and Riddler: These villains became recurring threats to the "Dynamic Duo". The Penguin was noted for his murderous intent despite his comical appearance, while the Riddler was defined by his obsession with intellectual superiority.12
• Two-Face: A gangster characterized by his grotesque scarring, patterned after the Jekyll-Hyde archetype.2
• Clayface: A serial killer inspired by horror cinema.2

In his very earliest appearances, Batman also faced more traditional threats, such as vampires, before the series shifted toward the costumed supervillains that would become central to his history.12