Jonathan Crane (Earth-4678)

"Remnants of Gotham, I have messages for you all. To the vandals who stayed behind to pick the still-warm flesh from Gotham's bones: have your fun. You are under my protection. To the cowards quaking behind the police department's walls: you will not be spared. And to Batman, I have already won. Emptied your city with a vial of toxin and a few threatening words. That's how little the safety you provided was worth. And when the dawn comes, when Gotham lies in ruins and I turn my gaze to the world beyond, the legend of the Batman will be worth nothing at all."

- Scarecrow

Dr. Jonathan Crane was taunted and bullied in his youth, and thus vowed to overcome his fears through the study of psychology and biochemistry on phobias and the nature of fear. Kicked out of the university he taught at for experimenting on human subjects, Crane adopted the identity of the Scarecrow, and armed himself with a specialized fear-inducing gas that makes a person's deepest phobia become a frightening reality. Scarecrow's ongoing reign of terror made him one of Batman's most recurring and psychologically dangerous foes.

When the Joker took over Arkham Island, Crane was released to cause as much death and chaos as possible. Using this to his advantage, Scarecrow tried breaking the mind of Batman again and again, only to fail. When attempting to poison Gotham City's water with his toxin, Crane was brutally mauled by the mutated criminal, Killer Croc. Seething with rage, Scarecrow exacted revenge on Batman and Gotham with his allies, the mysterious Arkham Knight and former assassin, Deathstroke. However, in the end, Crane's plan to break Batman's will failed, and he was forced to endure a dose of his own improved toxin. Reduced to a harmless shell, Scarecrow was left to suffer visions of bats.

Source
https://arkhamcity.fandom.com/wiki/Scarecrow