Warning! Spoilers ahead for Batman/Catwoman #4
Long after Batman's death, the Penguin is not only a free man but quite rich, most likely as a result of him never having quit a life of crime. Readers can easily come to the conclusion that the Dark Knight failed to take down the mafia boss when an aged Selina and her adult daughter Helena Wayne confront him separately in Batman/Catwoman #4 written by Tom King with art by Clay Mann.
Both of their confrontations with the Penguin are quite different. Helena comes to Oswald Chesterfield Cobblepot in hopes of uncovering her mother's relationship with Joker, while Selina arrives to ensure her daughter never finds out the truth. Each time, Penguin is surrounded by armed guards wearing ski masks, which automatically rules out the possibility that Cobblepot engages in legitimate business operations. Meanwhile, Penguin's continued success as a crime lord is made apparent during Selina's visit, as she finds him dining lavishly in what appears to be a highly secure room.
Unfortunately, Batman's failure as a vigilante crimefighter is not just confined to the Penguin. The future Gotham depicted in this issue is infested with criminals who are still at large regardless of how much time has passed. Based on Selina's age, one would surmise that the majority of them would have been executed or, at least, incarcerated by now. But that's not the case. The Joker is retired and has been living in his own home, while Tweedledum and Tweedledee are in a nursing home rather than a mental hospital, which makes it appear as though they were never charged with a crime. What's worse, the Ventriloquist is with them and Scarface. Meanwhile, Mr. Freeze is in stasis at his own lab and Clayface appears to be free. The only criminal behind bars is a villain who's identity remains hidden.
The state of these criminals proves that Batman failed to bring them to justice, most especially the Penguin, who is still very much an active and successful mobster. The real irony, however, is that the worst of them are dealt with in ways that Batman tried so desperately to avoid. This is exemplified when Catwoman murders the Penguin and Joker in cold blood.
During his heyday, Batman continually strived to ensure the criminal justice system would punish these villains within the fullest extent of the law. This vision did not include murder in any way. And yet, the mother of his child not only ensures these villains never see justice, but she also does the very thing Batman didn't want, all for her own selfish reasons. And that will forever be Batman's greatest failure.