Batman: Arkham - Why Aaron Cash Hates Killer Croc

screenrant.com:

In the Batman: Arkhamseries, there are few feuds as heated as Aaron Cash and Killer Croc's. The former Arkham Asylum guard turned Gotham City police officer harbors a deep fear and animosity toward Batman's reptilian foe, even when the Caped Crusader first meets him in Batman: Arkham Asylum. Though the two appear in nearly every game in the series, the story behind their rivalry extends back to before Arkham Asylum took place and speaks to just how honorable of a character Aaron Cash really is.

Batman holds a high opinion of Aaron Cash in the Batman: Arkham series, as Cash's psychological profile reads, "A Gothamite through and through, Aaron Cash has spent his entire working life serving the city's law enforcement and security services[...] He is a trusted friend of both Batman and Commissioner Gordon." Cash shows his duty-oriented nature throughout the story of Batman: Arkham Asylum by offering his help to the Caped Crusader despite the danger it puts him in, especially as an amputee who lost his left arm. Cash still occasionally shows his darker side when discussing Killer Croc, though, and even suggests that he kept him in solitary confinement and rarely fed him while working at Arkham Asylum.

Related: How Batman: Arkham Asylum's Founder Ended Up Its Second Inmate

Batman and players can understand Cash's hatred for Killer Croc after learning the origin of their feud, though. In the Road to Arkham comic that takes place prior to the events of Batman: Arkham Asylum, it is revealed that Killer Croc was the one who took away Cash's arm by eating it during a former breakout attempt — as was the case in mainstream DC continuity. Cash thus has every reason to despise the reptilian foe, but Killer Croc also taunts Cash