Batman has many iconic villains, with the most popular ones being twisted, broken and almost inhuman criminals in Gotham City's underworld. Others also take on an animal theme, with some being more literal than others. In the case of one foe, however, he works best when the man is more apparent than the beast.
Killer Croc can many times be portrayed as a completely animalistic supervillain. However, he didn't start off that way, and returning to his original form might be for the best. Here is why it would be better if Killer Croc goes back to his more human iteration.
Killer Croc wasn't Always a Monstrous Batman Villain
Making his debut in Detective Comics #254, Killer Croc was created by legends Gerry Conway, Gene Colan and Don Newton. Though this take would inform further incarnations, he was far from the borderline dinosaur man of later comic books and their adaptations. Originally introduced as Waylon Jones, he was merely a man who had been born with a rare skin condition. This gave him the appearance of having reptilian scales, making him look like something of a genetic throwback. Constantly tortured for this, Waylon would use his resentment to transform himself into a vicious killing machine.
Taking on a life of crime, Killer Croc would make quite a name for himself in Gotham. Poised to take over the city's criminal underworld, he was also written originally as being the killer of Jason Todd's parents. This made him a big deal, given his characterization. He wasn't just some savage beast -- he was a cunning crime lord who was just as proficient with firearms as he was with his fists. Sadly, later takes would significantly lower his intellect while also making him into an outright mutant of a man, very similar to how fellow Batman villain Clayface would change over the years. Now looking completely reptilian, the villain feels ill-fitting in the world of Batman. His beatdown at the hands of Bane only furthered his descent from relevance, but returning to his less inhuman incarnation could fix this.
Some might argue that having someone as "larger than life" as the modern Killer Croc in Batman's rogues' gallery helps liven things up. Unfortunately, this usually just results in the character being mere muscle, reducing him to a sort of boss battle character from a video game. There's little depth to this take on the villain, and he becomes so outlandish that he doesn't fit in among the mobsters and killers of Gotham. His original variant has far more potential though, as he could be utilized as a dark contrast to Bruce Wayne.
DC's First Incarnation of Killer Croc Has the Most Potential
Waylon Jones grew up in the exact opposite situation of Bruce, and in adulthood, he's far from a handsome, dashing playboy. Likewise, with few options at his disposal, he was forced to become an animal-themed wrestler and later crook just to survive. This contrasts with the incredibly rich Bruce Wayne choosing to become Batman, even if he's inspired by his own personal trauma. Likewise, one thing that Batman comics have done away with in recent years is having more outlandish villains operating as crime bosses. The classic Killer Croc employed his muscle and mind to become a criminal genius and making him merely skulk around in the sewers would prevent that.
These more relatable and grounded aspects could easily make for several great stories, especially if Croc begins building a criminal army with Gotham's disenfranchised. It'd offer an interesting commentary on Batman's many Robins while also showing how, despite Batman's best efforts, several disadvantaged kids simply fall through the cracks. It might not be as bombastic as seeing a crocodile on two legs rampage about like a mindless monster, but giving him this sort of characterization once more would certainly bring back the depth that was originally there when he was first created.