I am not particularly fond of the newer versions of Killer Croc in the Batman comic (especially in the Hush series). Overly reptilian incarnations of Croc don't seem to gel with the rest of the rogues gallery. The classic Batman villains such as Joker, Two-face and Scarecrow don't have to be mutated monstrosities to still be intimidating. Batman villains work best when writers avoid making them overly fantastic or super powerful. Instead the Batman villains should be "tragic and deranged humans". That fits so much better with Batman's own origin and psychology. Like two sides of the same coin.
For my version of Croc I wanted him to look a bit more generally creepy. I was imagining him as a guy with a skin disorder that turns his epidermis into hard scales. After years of ridicule and abuse for his appearance, he finally embraces his disorder. As a result he starts to mutilate himself (cutting off his nose, filing and capping his teeth, removing the skin on his cheeks, contact lenses, skin implants etc). My version of Croc wouldn't have as many super powers as his modern equivalent, but hardened skin that protects him and deadens pain, a brawler mentality, and a total lack of human compassion would still make Croc a mighty intimidating opponent!