For most comics in which he stars, Superman is the quintessential boy-scout, the all-powerful-all-knowing and all-loving God-like figure.
Every once in a while, though, Superman goes bad. And we're not talking, "Oh, he litters a bit," or "does a weird dance while wearing a black suit," bad. We're talking a Superman without a conscience. A Superman who makes Batman and Lex Luthor look like Care Bears. Even in canon, non-Elseworlds comics, the Man of Steel has done some messed up stuff. Such as...
This one needs a little backstory. See, back in the nineties there was a comic called The Authority that asked, "What if the Justice League was useful?" It was full of Justice League equivalents -- totally not ripped off, squint and you'll see the differences, versions of DC superheroes -- who fought dictators, killed those who needed to be killed, and even gave God an aneurysm. They were really, really cool.
Their brash, no-nonsense method of crimefighting was meant as a rebuke to the soft and cuddly, "Let's throw this serial killer in an easily escapable jail and cross our fingers he doesn't get out again," moral code that you could see in DC.
Well, DC -- despite owning the comic company that published The Authority -- didn't like that. Especially those who were in charge of Superman. Thus came "What's So Funny About Truth, Justice, and the American Way." It introduced The Elite, who are basically send-ups of The Authority, who were themselves send-ups of the Justice League. This is what happens when comic book continuity runs over 70 years.
The Elite were a team that was dedicated to eradicating evil, and had no concern for the moral sanctimony of cape wearing weirdos. Superman -- perhaps jealous that there were finally superheroes more unaccountable than himself -- decided to stop them, peacefully.
When that didn't work, Superman killed every single member of the Elite.
Well, okay, Superman left the leader alive, but that was mostly so he could lobotomize him.
Except, uh, just kidding? Superman reveals that he only tricked the Elite into thinking he was killing them. Instead of a stern lecture, Superman decided to prove to these kids once and for all that killing evil people was wrong, and he did so by... killing all of them. Except not really.
The Elite, coming to the correct conclusion that Superman was too messed up to deal with, decided to quit before the Man of Steel actually decided to really kill them. The moral of the story: Killing is never right. But psychological torture? Well, that's juuust fine.
Superman sometimes has exceptions to his no-kill rule. Gods, Kryptonians, and whatever the hell Brainiac is all seem to be on the table -- but human beings are a non-starter. Except, maybe, for Heather Kelley. Heather was a reporter for the Daily Planet, working alongside Clark Kent. One day Heather was minding her own business when an alien being from Krypton latched itself onto her body and became a mindless beast bent on destruction.
Superman, seeing there was another Kryptonian for him to kill, made a beeline for the disaster epicenter only to discover the epicenter was his actual friend and co-worker. So, obviously, he attempted to figure out a way to save her, right? Well...
Instead of thinking of another way, Superman just asked for her forgiveness and shot super fire beams out of his eyes. Now, to be fair, Heather doesn't actually die. The heat vision -- coincidentally -- broke the Kryptonian beast's hold on her. But that is obviously not Superman's intent. As is revealed later in the comic, Superman basically admits he was willing to kill one innocent person for the good of the many.
So remember this in-canon bit from Superman when people tell you that he doesn't kill. Heck, he'll even kill his own friends if he has enough justification. Of course, that's not the most messed up thing that Superman's done. Far from it.
If DC has an equivalent of Marvel's Thanos, well, it's the original bad boy Darkseid. But Mongul is up there, too. If you need an entry point to the yellow and purple beast, there's no better place to start than "For the Man Who Has Everything," created by Watchmen team Alan Moore and Dave Gibbons.
Where does Superman fit into all this? Well, it's his birthday. He wakes up, and instead of being greeted with the cold static crystals of the Fortress of Solitude, Superman finds himself on Krypton. It didn't blow up after all. Everything was a horrible dream. Kal-El has children, a wife. His father is there, and so is his mother. Everything is as it should be.
Of course this can't be real. It turns out that these false visions of Krypton are being suppliedby a thing called the Black Mercy, a telepathic plant that has him in its thrall. While the plant slowly kills Superman, it feeds him perfect dreams. This is the work of Mongul, who delivered a gift box to the Fortress on Supes' big day. Of course, Smallville's biggest dope decided to open it.
Batman, Robin and Wonder Woman team up to help break him out of there (while fighting the nigh-impervious Mongul). In order to leave the Black Mercy, Superman has to admit to himself that his perfect life is fictional, and so he watches as Krypton is destroyed, once again and he holds his son -- who doesn't exist -- in his arms.
When he comes to, he's righteously pissed and beats Mongul up but good.
You'd think he'd be happy getting to see his planet blow up again, knowing how terrible of a person he is, but apparently he only likes it when he's the one causing all the deaths.
After some punching, Mongul defeats Supes. Kills the Justice League, and lords over the entire Universe because... during the fight with Superman, Mongul fell against the Black Mercy and it ensnared him into a waking dream that will last forever.
Superman, Batman, Wonder Woman and Robin all them decide, "Eh, sounds good to us," and leave Mongul like that. The character wasn't seen again until the DC Universe was rebooted, and so he continued to live in his false hell, of which he was king. Because if you piss off Superman, that's what you get -- a fantasy wasteland of your own making.
Superman isn't just a dick when it comes to other universes, he can be a dick in canon comics too. If you've been on the internet long enough, you might remember there's an entire site dedicated to the big blue boy scout torturing the people he loves most..
For instance, when he sees a kid littering and leaving his bike on the stairs, what does he do? The only reasonable thing, of course, which in this case means stealing every bike in the neighborhood and throwing them on top of the bike belonging to the mildly delinquent child. This teaches us a valuable lesson: Don't piss off Superman.
That's literally just child's play. What Superman does to Bizarro in the latter's first appearance is far worse. Remember, Bizarro is basically this busted-up version of Superman who often means well but can't properly express that through his actions. As a result of his social ineptitude and ghastly appearance, even Ma Kent can't bear to look at him.
This issue takes place when Superman was still Superboy, so if you had to guess, how would little Clark Kent solve this situation? Laser vision? Charles Atlas catalogs? The power of friendship? If you guessed anything other than "kill Bizarro because he's ugly," you might not be paying attention.
Even when he got older though, he turned on his best friends with all the ferocity of a sociopath with the powers of a demi-God. There was that time he adopted Jimmy Olsen only to mock his new son's present and incinerate it with his eyes.
If you want to know what sorts of nasty shenanigans Silver Age Supes got up to, imagine the cruelest thing a high school bully would do, and then add super powers.
The worst thing Superman has ever done to Lois Lane? It might be the time he dressed up as Satan himself and convinced Lois Lane to sign a contract forfeiting her soul in exchange for a guaranteed marraige to the Man of Steel.
And this is the lawful good, canon Superman. Imagine what an evil version could do.
Injustice started out as a fighting game from the developers of Mortal Kombat, only in place of Scorpion and Sub-Zero are various DC superheroes. The creators of the spine-ripping Fatalities naturally wanted to put their own dark spin on their game, which centers on an evil dictator Superman who rules over a shattered world.
You wouldn't expect much from a tie-in comic to a game like this, but the Injustice series has put out some great stories.You might have seen the image that started it all -- after being tricked into killing Lois Lane, Superman kills the Joker.
But hey, he's the Joker, right? He deserved it. But you can't exactly say that much for Green Arrow.
What'd Green Arrow do aside from accidentally graze Pa Kent with a projectile and also have a mediocre TV show? Superman remains unrepentant and proceeds to let loose, beating the world into submission with his dictatorial iron fist -- at one point, he even heat-visions a whole building of protestors. Injustice Superman and his minions are responsible for the death of Nightwing, (good guy) Lex Luthor, Shazam, Hercules, Martian Manhunter, Huntress, Dick Grayson, Captain Atom, and more people you don't recognize. And Hawkman!
Of course, this isn't the first time Superman's been an evil monster with dictatorial ambitions. In another world, there's Overman, who is head of a regime established by Adolf Hitler after winning World War II. But in that world, where Superman is a literal goddamn Nazi, he ends up feeling bad and helping take down the regime he's a part of. That's right -- Nazi Superman is a better person than Injustice Superman. Sit on that for awhile.