While it's true what they say about Spider-Man spinning a web any size and catching thieves just like flies, Peter Parker has been has also been put through some of the worst personal tradgedies imaginable. Sure, he might be more famous for having girl troubles and money problems, but Spidey has also had to deal with horrors like drug abuse, suicide, and cannablism.
This darkness can and has driven Spider-Man over the edge, and while he doesn't turn into a full on villain, well... sometimes it's a bit hard to tell how close exactly he is to that line. Here's the kind of stuff we're talking about:
Kraven's Last Hunt is considered one of the best Spider-Man stories ever, and that's partially because of how brutal it is, even for the edgy 90s. It all centers on Kraven, a man-hunter straight out of "The Most Dangerous Game." Before the first issue of the story arc is over, Kraven has already terrorized, humiliated, and definitively defeated Spider-Man by burying him alive.
For two weeks, Kraven wears Spidey's classic black suit and fights crime, proving once and for all (in his eyes, anyway) that he is the superior human specimen.
After Kraven destroys a villain that Spider-Man could only barely beat with the help of Captain America, he finally feels content and complete. The hunter could have killed Peter Parker at any time, but that was never his plan -- he only wanted to reach his own personal peak, and know that Kraven won, once and for all. In his mind, there was nowhere else to go. And, having accomplished everything he ever wanted, Kraven killed himself. It's not even over yet.
Years later, Kraven's wife and daughter would gather together all of Peter's villains and throw them at him one after another, pelting him like so many putrid water balloons. Their goal was to gain a sample of Peter's blood so they could use it in a dark ritual to bring Kraven back to life. What actually happened was that Peter's clone (he has... a couple of those) got massacred and drained of blood while Peter was buried alive... again.
Enraged, Peter put on his black uniform once more and destroyed every villain he could find until finally making his way to Kraven HQ. It was at that point Spider-Man used his sticky wall-crawling ability to literally rip Mrs. Kraven's face off.
Afterwards, Mr. Kraven took his family to the Savage Land, murdered Mrs. Kraven and sent one of his children off to hunt the other. Since then, Kraven has become best buddies with Squirrel Girl, the peppy young girl who talks to squirrels, because comics make less than no sense.
Sandman has proven himself to be one of Spider-Man's most memorable rogues. Flint Marko is strong, evasive, and smarter than your average burglar -- and he's also a giant pile of dirt that can take any shape. Maybe that's why Sandman realized that he'd be better off ditching the villain business and joining the Avengers.
Flint became a villain again soon enough, but this time around he was lighter, softer, more interested in money than evil, and one who had buttloads of sympathy. What does Spider-Man do with this information? Why, exploit it to torture one of his biggest enemies, of course.
Teaming up with Black Widow and Silver Sable, Spidey figured out a way to manipulate Flint's transformation, a lot of which involves planting subconscious ideas to mess with Sandman's mind.
This was all in service of finding the one speck of dust that contained Sandman's essence, a tiny soul needle in a giant body haystack. As it turns out, the easiest way to appeal to get someone to show their heart to you is to mention the only thing they care about in the world. In this case, it's Sandman's daughter.
In order to steal Sandman's soul, Spider-Man proved that the villain had one in the first place.
So why was Spidey doing this, again? Let's back up -- just before the Superior Spider-Man era, Doc Ock was attempting to 'save the world'. Naturally, to Spider-Man this looked a lot like Doc was trying to destroy the world, so he tried tracking down one of his greatest enemies, only to run into Sandman.
And so, working with an assassin -- because, hey, why not -- Spider-Man ripped the soul sand out of Sandman and locked it in a jar. And that's when things got really messed up. In order to get Sandman to talk, Spider-Man watched as Silver Sable poured acid all over a greatly diminished sandman. This "enhanced interrogation" could have literally killed Sandman and wiped out his soul forever, and webhead almost let it happen.
Soon after this storyline, Spider-Man would be killed and his body taken over by Doc Ock -- even then, he never quite managed to do anything that evil.
A good rule of thumb: Whenever Peter is wearing the black suit, you can be sure the story is going to be dark. When Peter first got the suit it was an alien symbiote. After he took it off, he kept the black suit's design because it looked stylish? But then the symbiote merged with a dude for a hate-on for Peter and became Venom, who proceeded to attack and nearly kill Mary Jane. After that, MJ had an understandable distaste for the look, so for Spider-Man to don the suit again is a big deal. It's become short-hand for Peter letting the monster loose.
And in Back and Black, lets go and then some. See, Spider-Man unmasked himself back during the first Civil War event, which led his enemies to come after his loved ones -- because, hey, they don't have Spidey senses. Soon enough, Aunt May was shot by an assassin that turned out to work for the Kingpin. At the same time, Peter was being hunted by the authorities (because he eventually joined the anti-government side during the Civil War), so when Aunt May fell into a coma he couldn't even visit her.
What else is a pent up youth with a ton of rage to do? Did you say throw on some black clothes and go full-on rage goth?
After donning the black suit, Spider-Man gives the hitman a savage beatdown and then breaks into prison to confront Kingpin. Then he takes his mask off and beats Fisk within an inch of his life, all the while mocking him for thinking he could ever be strong. He then leaves, with blood on his hands.
But it could have been much worse. There's a What If? In which Mary Jane gets shot and killed. Peter does much the same -- dons the black suit, goes ballistic -- but here he actually kills people, starting with icing the assassin who shot MJ and ending with Kingpin, who he literally eviscerates by ramming his hand through Kingpin's chest.
And then he gets arrested. Which is somehow a brighter ending than what happens in the actual Back in Black storyline.
In canon Back in Black, Peter meets up with Mary Jane and the two are approached by the literal devil.
Spider-Man makes a literal deal with the devil, sacrificing his and Mary Jane's love, and their future unborn child, to save Aunt May. The only punchline here is that this comic is still canon.
Dead No More was the rather fitting title to a story about a bunch of dead people suddenly coming back to life. Not just a couple people, not just heroes or villains -- almost everyone who died in comics came back. J Jonah Jameson's wife, Gwen Stacy, Stacy's dad, Rhino's wife, and also all of the heroes and villains who had died beforehand.
This was eventually revealed to be the work of the Jackal, a character who had previously made multiple clones of Peter Parker, including Kaine -- the one who Kraven killed -- and Ben Reilly, who assumed Peter's role as Spider-Man, before dying at the hands of the Green Goblin. The Jackal hadn't been seen for awhile, but now he was back, and he made a "new" Gwen Stacy.
After Spider-Man found out what was going on and confronted the Jackal, it turned out he wasn't Miles Warren, the original Jackal. It was actually Ben Reilly, driven mad after being brought back to life and killed again and again and again and again.
It's a pretty big heel turn for someone who was the only Spider-Man around for a couple of years. Apparently Ben was being tortured for years, cloned and recloned, before finally snapping and turning the tables on his captor. Then Ben took the mantle of the Jackal and decided to bring back everyone. Everyone.
Which doesn't sound bad, except for the clones slowly decaying while still alive. If the clones didn't do whatever Reilly told them to do, he would withhold a serum that kept them alive. He used the procedure to bring back tons and tons of people, so that he could manipulate them and their loved ones.
Because this is a comic, Spider-Man eventually stopped him... and by stopped him, we mean, killed almost every single clone that was out there, leaving (among thousands of others) J Jonah's wife decaying in his own hands.
Some clones managed to survive the process -- including Doc Ock who started working for Hydra with a new clone body that had all the powers of Spider-Man. Thanks a lot, Scarlet Spider! As for Ben Reilly, he escaped, killed the original Jackal and moved to Vegas, which is actually the only way a story this dark could truly end.
Lastly, let's roll back to the Gauntlet storyline -- you know, that era mentioned earlier, in which Kraven's wife was throwing supervillains at Peter Parker left and right. The "Shed" arc saw the return of one of Spidey's oldest villains/best friends: The Lizard. For those of you who blocked out the Amazing Spider-Man movie, the Lizard is actually Curt Connors, a man who lost his arm and ended up turning himself into a scaly monster in an effort to regrow his appendage. You know, comic book stuff.
At this point in the character's life, Connors had managed to subdue the Lizard part of himself into his own subconscious, but in the process he became a pariah in the scientific community. Connors also lost custody of his only child, Billy, who also started hating him because children have something against giant reptiles.
It was during the Gauntlet that Connors was driven to his breaking point -- stress over his failures at work and his jealousy over a girl he was crushing on led him to experience super Lizard symptoms. All it took was one person stopping him from taking his special "anti-Lizardification" serum and boom, the grim and green was back.
Killing Connors' boss and co-worker wasn't enough. The Lizard part wanted full control, and decided it had to destroy Connors, who it saw as a rival male in its territory. You can probably guess what lizards do the rivals of their young. Oh, but don't worry, Spider-Man arrived in time, stopped the Lizard, and Billy awoke Doc Connors, and everything was okay. Or, at least, that's how it was supposed to go. However, the Kraven family saw this predictable, comic-booky sequence of events ahead of time in a vision, and decided to change all that. So the Kravens kidnapped Billy and stalled Spider-Man just long enough for the Lizard to get his way.
And the Lizard did was Lizards do: he ate Billy. The Lizard ate his own son.
Connors fully lost control of himself at that point, completely shutting down and allowing the Lizard to take over. If Connors effectively "died" here too, it would have been a mercy. But then the Lizard got punched real hard and Connors regained control -- only now he wasn't able to revert to human form. So what was left was a human man in a monster body, living with the knowledge that he was digesting his son at that very moment. Now why wasn't that in the movie?