Denny O’Neil, one of the most influential minds to shape the lore of Batman in the late 20th century, is dead at the age of 81.

According to his family, O’Neil passed away from natural causes during the night on June 11th. He is best known for his work on Batman starting in the 1970s with the team of editor Julius Schwartz and renowned artist Neal Adams.

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The trio was responsible for bringing the Dark Knight back to his dark roots and out of the doldrums of the campiness synonymous with the Adam West TV series and the Super Friends cartoon.

An editor of DC’s Batman titles for 15 years, O’Neil wrote some of the more notable ones such as Batman, Detective Comics, and Batman: Legends of the Dark Knight.

He was also instrumental in the creations of Ra’s al Ghul, Talia, Dr. Leslie Thompkins, Azrael, and Richard Dragon. The first three became staples of Batman: The Animated Series.

And he helped modernize Joker and Two-Face while also overseeing the murder of Jason Todd by the former in the Death in the Family story. The decision to kill Robin met with some public pushback from fans.

Batman: A Death in the Family - DC Comics

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O’Neil and Adams spearheaded revivals of other heroes including the infamous pairing of Green Lantern/Green Arrow. The two traveled the country as best friends and a bit of an odd couple. Green Lantern was a square by-the-book cop whereas Arrow was more of a free-spirited liberal.

Green Lantern/Green Arrow didn’t last but was around long enough to shock readers with the revelation GA’s sidekick Speedy was a heroin addict.

At one point, O’Neil tried to reinvent Wonder Woman as a formidable butt-kicker without powers. The take didn’t sit well with Gloria Steinem and was canceled.

Other DC books to his credit are Justice League, The Question, Armageddon 2001, and the one-shot Superman vs. Muhammad Ali. O’Neil once worked for Marvel too, penning Amazing Spider-Man, Iron Man, and Daredevil. He was the one who brought Frank Miller onto the Man Without Fear.

At Marvel, O’Neil helped create Madame Web, Iron Monger Obadiah Stane, Lady Deathstrike, and Hydro-Man. He is also credited with the concept for Transformers and naming Optimus Prime.

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He plied his trade later for TV, writing episodes of G.I. Joe: A Real American Hero, Logan’s Run, Superboy, and Batman: The Animated Series (both of which stream on DC Universe).

O’Neil shared his knowledge in the how-to book The DC Guide to Writing Comics and opened up about his experiences in comics in the documentaries Comic Book Superheroes Unmasked and Legends of the Knight.

Aside from writing and editing, he taught at Manhattan’s School of Visual Arts and was on the Hero Initiative’s Board of Directors.

His legacy and contributions were celebrated in 2019 when May 25th was declared “Dennis O’Neil Day” in Phoenix; and again in 2018 when the Jimmy Carter Presidential Library made him key speaker at the”Comic Books and Social Justice” weekend.

Creators and organizations have been paying homage to the legend on Twitter.

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