Killer Croc Went from a monster to a misunderstood loner.
Among Batman's changing rogues gallery, Killer Croc is among the more prominent ones. Killer Croc was only an over-sized criminal with a skin ailment concept when he first debuted. He was just nasty and thought only about acquiring more authority. Though they were only citizens, he had absolutely no problem executing Jason Todd's biological parents. But Croc developed over time into something more, moving from a sometimes-cannibal thug to a hero of the oppressed.
Killer Croc has developed from a wannabe gangster to someone who really tries to help the less disadvantaged in recent years. In Killer Croc's past, he has been a guardian of less fortunate people many times. For the odd and unusual people living in Gotham City, he even attempted running his own hotel. Although Croc is still more often than not a villain, he has also been shown as someone who just wants to be left alone and is ready to provide someone else refuge from society.
From Villain to Hero - and Back Again, Clayface Went
Not one other major villain who underwent a heroic turn was Clayface. Detective Comics run by James Tynion IV revealed that Clayface's brain spans too far upon transformation. Clayface therefore literally loses his capacity to distinguish good from wrong. Batman understands this, so he knows that during the previous few years Clayface has not been accountable for any of his murders. Armed with this knowledge, Batman chooses to teach Clayface as a Bat-Family member under his wing, therefore transforming Clayface into Batgirl's friend.
For Clayface, the disclosure that he lacked complete control over his actions was the ideal tragic turn-around. Having spent his whole adult life performing, he discovered he had powers he couldn't control his body anymore. Since he literally couldn't differentiate right from wrong, he would act out and engage in crimes. Although Clayface had a fantastic run as a hero, DC finally walked this retcon back, therefore ever since, Clayface has remained a villain with no real reference to his past heroic arc.
Gotham's Classic Villains Are Not Pure Evil Anymore; DC Comics Are Better For It
Although these characters began out somewhat one-note, Batman has some of the most legendary Villains in comic book history; their great popularity has resulted in their complexity throughout the years. Batman's rogues have more complexity than ever before and are better characters for that change than just robbing banks or aiming for random murder.
Particularly cleverly, Poison Ivy #22 by G. Willow Wilson and Haining highlights Batman's unexpected development of his foes. The wicked Jason Woodrue in this narrative is trying to assassinate Poison Ivy and even targets a harmless civilian friend of hers. The sheer indignation from Killer Croc and Poison Ivy at Woodrue threatening to harm an innocent surprises Woodrue.
Harley Quinn has become a quite different character.
Harley Quinn is without a doubt the ideal illustration of Batman's rogues expanding and evolving with time. Harley originally made appearances in Batman: The Animated Series, where she was merely a humorous henchman for the Joker, but she became so well-liked that she was returned repeatedly. From one of the Joker's associates, Harley Quinn evolved into one of the most iconic comic book characters worldwide. She has starred in live action TV series and films as well as various animated films and her own animated TV show.
Harley developed as a character more than everyone else. She left the Joker and started her own proving she doesn't need the Joker to be popular. She routinely has her own comic series and has been among DC's best-selling characters overall. She moved from a one-note character blindly committed to the Joker to have intense conflicts over her trauma and past as a super-villain. Only because DC invested time to make Harley more than just the Joker's nasty sidekick could Harley try throughout the years to atone for the horrible things she committed.
Red Hood Is One of Batman's Most Compelling "Villains" by Jason Todd
Even if a complicated villain, Jason Todd's debut portrayal as Red Hood was essentially one. Because of his grief and the tragedy of his death and return, he attacked Batman and the Bat-Family at every chance he got (while also trying to save Gotham using his own deadly methods, of course). Red Hood's depth was seldom extended beyond being a big villain with extensive knowledge of how the family operated, even with his significant history with Batman and the Bat-Family. Red Hood rejoined the Bat-Family as a full-fledged hero only once the revamped New 52 continuity launched.
Fans interested in seeing Jason Todd as a true Batman opponent and villain should check out Batman: Under the Red Hood by Judd Winick and Doug Mahnke, as well as Grant Morrison's run on Batman and Robin from shortly before the New 52 reboot. In current, Dawn of DC-era comics, Jason still has moral conflicts with the Bat-Family, but Red Hood struggles with his own desire to use lethal force on criminals while also still being a hero. He was shunned from his own family and wanders between teams, including the Outlaws, nonce. If Jason had remained a generic villain, then it would've been a true waste of his character and the history he's been through.
Over the Years, Batman's Villains Have Developed
Nearly all of Batman's enemies began their stories as single goal-oriented characters. Killer Croc simply wants to be a major crime lord. Harley Quinn just wanted to serve the Joker. Clayface just wanted to rob banks and kill people. They had no real depth or tragedy to them. But DC has been taking steps in the last few decades to give these characters actual goals and wants. These changes make their conflicts with Batman all the more fascinating, because it's no longer a case of just random criminals committing crimes, but damaged people trying to find their place in the world.
Poison Ivy #22 is available now from Dc Comics!