Sometimes Scarecrow is used more as plot device for interesting visuals rather than as a villain.
Scarecrow is a master of fear but he can also be intimidated. Fear of pain, fear of death, fear of having your own work destroyed.
Batman instills the fear of pain onto other criminals
His villains instill the fear of death onto their potential victims.
Scarecrow makes people hallunicate their fears.
Scarecrow does not make people afraid of him, he makes people of afraid of their own worst nightmares.