Waylon Jones, better known as Killer Croc, is a recurring supervillain in DC Comics, recognized as one of Batman's most physically imposing adversaries. He first appeared in a cameo silhouette in Detective Comics #523 (February 1983), with his full debut occurring shortly thereafter in Detective Comics #524 (March 1983), created by writer Gerry Conway and artist Gene Colan. Born with a rare genetic disorder known as regressive atavism or epidermolytic hyperkeratosis, Jones developed scaly, reptilian skin and enhanced physical traits from birth, enduring relentless bullying and abuse that shaped his path toward crime. His condition progressively worsened, granting him superhuman strength, durability, sharp claws and teeth, regenerative healing, and amphibious capabilities, while often diminishing his intellect and humanity.

Initially portrayed as a cunning underworld figure in Gotham City, Killer Croc rose through the criminal ranks by leveraging his intimidating appearance and brute force, working as a circus performer and enforcer before fully embracing villainy. He attempted to seize control of Gotham's organized crime in early stories, clashing repeatedly with Batman and occasionally Robin (Jason Todd, whose origin intertwined with Croc's pre-Crisis narrative). His sewer-dwelling lifestyle and cannibalistic tendencies in certain depictions solidified his reputation as a monstrous threat, with confrontations emphasizing his raw power against Batman's strategy and gadgets.

Over time, Killer Croc's character evolved to incorporate greater tragedy and complexity, shifting from a calculating mobster to an increasingly bestial figure in post-Crisis and modern continuities. Notable developments include his infection with a devolutionary virus in the "Hush" storyline (2002-2003), amplifying his reptilian traits; his recruitment into the Suicide Squad for high-risk missions; and explorations of his vulnerability in arcs like Arkham Asylum: Living Hell (2004). In New 52 and Rebirth eras, portrayals often highlighted his isolation and occasional sympathy, positioning him as a misunderstood outcast while retaining his role as a formidable, primal antagonist in the Batman mythos.