Super-hero comics have provided some brilliant cliffhangers over the decades. Choosing 10 of the best, most significant cliffhangers is a tough job, so let's narrow it down to the "Big Two" comic book companies, Marvel and DC Comics. Between them, they have provided some cliffhangers that not only brought us back for more, but have influenced comics, television, and the movies.

1. Crushed like a bug

The Amazing Spider-Man #38, 1966 #31-33, 1966

One of the super-heroes' worst enemies was the Comics Code Authority, the tough censorship body, which even frowned at cliffhangers because the villains were not brought to justice in the same comic where they committed their crimes! Marvel Comics' Spider-Man was one of the first comics to rebel against this, allowing villains to escape until the next issue. But even when he won, Spider-Man could still be left with a great cliffhanger. One of the most popular stories (recently voted the second most popular Spider-Man story ever, 46 years after it was published) finished with a doozy: With his Aunt May in hospital, dying of radiation poisoning (due to a blood transfusion he gave her), he tries to get the antidote, but is stopped by the villainous Dr. Octopus. Angrier than ever, Spider-Man destroys Dr. Octopus's lab. Though Dr. Octopus is defeated, tons of metallic debris falls on Spider-Man, leaving him trapped. As water starts to flood the structure, the serum remains just out of reach. (In the next issue, he frees himself and grabs the serum just in the nick of time.)

2. The coming of Galactus

The Fantastic Four #48, 1966

Afraid that the popularity of super-heroes would not last forever, Marvel editor Stan Lee and artist Jack Kirby (who co-wrote The Fantastic Four) upped the ante by creating the ultimate super villain: Galactus, a godlike, 28-foot-high being who survived by consuming the energy from planets. In the first cliffhanger of this story, he announces that the Earth is doomed. The cliffhanger was powerful enough to change story structure in comics, so that countless stories have followed this formula, revealing the villain on the final page of the first issue... then finding a way to stop him over the next few issues. After Galactus, however, villains would rarely seem so threatening.

3. "Prepare for... my ultimate REVENGE!"

Captain America #115, 1969

This one wasn't quite so influential, but it's one of my favorite cliffhangers ever (so there). This comic ended with the hideous Red Skull using the magical Cosmic Cube to transform Captain America into the Red Skull, while the Skull himself transforms into Captain America. The Captain's girlfriend Sharon runs to the villain for protection, unaware that, deep down, he's a monstrous war criminal. The hero himself is stuck with a skull-like visage and a girlfriend who thinks he's an evil monster, but being an altruistic good guy, he's not just thinking of himself. "What will happen to her," he thinks, "and to all MANKIND... while the world's DEADLIEST MENACE can walk among men... as CAPTAIN AMERICA?!!" The idea would later be done in television and movies (like Face/Off), but perhaps the comics did it best.

4. "You're really a junkie?"

Green Lantern / Green Arrow #85, 1971

The Comics Code had decided that drugs were off-limits for comics – so much so that, when Marvel did an anti-drugs story in Spider-Man (at the request of the U.S. Department of Health, Education and Welfare), it wasn't given the stamp of approval. (That's another story that can be found here.) After this, the rule was relaxed. The idea of a super-hero who used drugs, however, was unthinkable... until Speedy, the Green Arrow's ward and young sidekick, confessed all to his anti-junkie guardian. Speedy's drug habit came as a shock not only to the Green Arrow, but to his readers as well. He was a respected sidekick, and a valued member of the Teen Titans. Writer Denny O'Neill, who based many powerful stories around Speedy's addiction, later worked for Marvel Comics – writing stories about Iron Man's alcoholism that, once again, did not trivialize the issue.

5. "Now it's MY turn!"

Uncanny X-Men, 1979

A classic cliffhanger leaves our hero in a terrible predicament, making us want to read the next issue for an answer to the question "How will he get out of this one?" Some cliffhangers, however, make us want to read on for other reasons. One of Marvel's best-remembered cliffhangers happened when the evil Hellfire Club ambushed the X-Men, pounding Wolverine under a building, and defeating everyone else one by one. In the last page, when all seemed lost, the savage (and basically invulnerable) Wolverine reappeared from the sewers. "Okay, suckers – you've taken yer BEST SHOT!" he says. "Now it's MY turn!" What did he do next? You would have to read the next comic to find out how he handled those creeps – and, of course, who could turn down such an offer? Soon, X-Men was America's top-selling comic book, and Wolverine was polled as Marvel's most popular character, the guy you can really depend on when the going gets tough. That cliffhanger was frequently imitated – on the comics and on TV. (Memorable example: The famous cliffhanger in Buffy, in which Giles appears as the last hope against the seemingly unstoppable Willow.)

6. The end of the universe

Crisis on Infinite Earths #4, 1985

DC Comics decided to reboot their whole universe (and improve their sales) in Crisis on Infinite Earths, a series in which the universe (in fact, several parallel universes) were being wiped out by a mysterious wave of anti-matter. The story was meant to last for 12 issues, but in the final pages of the fourth issue, the universe is clearly erased from existence. The final words: "To be continued --?" Of course, they were saved, and a new universe was forged from the wreckage. (This universe lasted until 2011, when the world was reset yet again. Once more, starting afresh was good for sales.)

7. "I did it 35 minutes ago."

Watchmen #11, 1987

Many consider Alan Moore's super-hero series Watchmen to be the greatest super-hero comic ever. It certainly ranks among the most intellectual, discussed in university courses and even appearing (as a graphic novel) among the New York Times bestsellers. Fittingly, the main "villain" (though it's too simple to call him that) was Ozymandias, a former super-hero. While he wasn't as strong as some others, he had a far more dangerous power: super-genius. In one issue, in his hideout in Antarctica, he revealed to some of his former allies that he had created an "alien being" that he planned to teleport into Manhattan, killing half of the city in the process. It was a classic situation: a bad guy gloating about his terrible plan to the heroes, so they have time to stop him. "When were you planning to do it?" asks Nite Owl. But that's where it gets interesting: "Do you seriously think I'd explain my MASTERSTROKE if there remained the slightest chance of you affecting its OUTCOME?" says Ozymandias calmly. "I did it thirty-five minutes ago." In the next issue, half of New York was destroyed (a scene that was changed slightly for the film), and it was clear that Watchmen was not your average super-hero comic.

8. "Can he possibly be alive?"

Batman #427, 1988

DC Comics wasn't sure about Jason Todd, a.k.a. Robin. Since ha had become Batman's sidekick (to replace Dick Grayson, the original Robin), he had not been popular, so they tried something new: they left his fate to the readers. Writer Jim Starlin and artist Jim Aparo prepared two stories for publication – one in which he was killed by a bomb, one in which he survived – depending on the readers' votes. Result: he was killed. In 2005, the hit TV show Law & Order took DC's lead, using audience votes to determine the fate of child killer Nicole Wallace (Olivia D'Abo). Though she was a villain, the viewers spared her life. Robin, one of the good guys, was executed by comic book readers. Perhaps Batman fans are more bloodthirsty than Law & Order fans? Whatever the case, Robin returned to life years later (as super-heroes tend to do), so the readers' dastardly plot was foiled after all.

9. Clark Kent reveals his identity

Action Comics #662, 1991

One of the essential parts of the Superman legend is that few people know that he is Clark Kent – not even the woman he loves. Even 54 years later (in reality, not in the comic book world), with Lois Lane finally engaged to Clark, she was still unaware of his double life. On the final page of one comic, however, he revealed the truth to a startled Lois, leaving us to wonder "How will she take it?" She was surprisingly happy to find that her fiancé was actually Superman. Readers took slightly longer to get over their shock – and the proof that even Superman, after all these decades, can still try something new.

10. Unmasked

Thunderbolts #1, 1997

With other Marvel super-heroes presumed dead, the Thunderbolts were introduced as a new team to fill the gap. Soon they had their own comic, promoting them as "all-new heroes" and "the next Avengers." But at the end of the first issue, after a successful day's crime-fighting, their patriotic leader Citizen V revealed in the privacy of their HQ that he was actually Baron Zemo, a Nazi villain from the Captain America comics. His teammates were also revealed: members of the Masters of Evil, who had fought the Avengers on many occasions. Their plan: win everyone's trust (which they were already doing), then rule the world. It was considered one of the great twists in comics. Of course, the real heroes returned soon enough, and Zemo was defeated (though some of his pals liked playing hero so much that they changed sides).

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Thanks to commenter Kendall for pointing out the error in the Master Planner Saga issue numbers! #38 was great, but it was no #33.