People always see Batman as the prototypical grim n' gritty hero, but he can't compete with the Flash. For a supposedly "fun" superhero, the Flash has committed a surprising amount of horrifying atrocities. Sure he's done a lot of good too, but to be fair he's also been around for almost 80 years. We're not saying the Flash is evil, it's just when you can read about a thousand books in the time most people can read this word, sometimes your decisions can be a bit... rash.
Most superheroes have this whole "No Killing" rule, and you'd think the one person who'd take that the most seriously is the Flash since, you know, he can move so fast that bullets seem like sloths. He can incapacitate people, harmlessly, before they even realize he's there. What does he have to worry about? Plus, his whole optimism and pep? C'mon, he's obviously the one who is the least brutal. Ah, friends, but remember, he's also a cop.
Despite that, the Flash is still pretty chill about killing when it comes to most of his villains, with one exception: Zoom. See, Zoom (aka Professor Zoom or Eobard Thawne or the Reverse Flash), is one of the Flash's most powerful and terrifying villains. He's as smart as the Flash, but faster, and with no morals whatsoever. Zoom even went as far as to mess with his enemy on his wedding day, and getting married is already stressful enough as it is.
Oh, and did we mention he's totally obsessed with the Flash? We mean, take the most misogynistic "crazy ex-girlfriend" story you can find, and then swap out the names and bam, you've got Thawne's relationship to Allen. The Joker's love for Batman is often buried in subtext, but with Zoom and Flash, the infatuation subtext is mostly just text. Zoom even got jealous enough to kill the Flash's first wife just because The Flash wasn't paying enough attention to him (and, because, you know, Thawne's a supervillain and all supervillains need to fridge at least one wife to stay around, legally). And so when Flash was slated to give marriage another shot, who showed up to write creepy messages in the sand?
The Flash took that first loss pretty hard, but he just beat up Zoom. However, the next time Zoom came around, he went to kill The Flash's new fiance,and she was like so much hotter, so this time the Flash made sure to stop him. By snapping his GD neck.
Yes, it was to help someone else, and you could argue it was in "self-defense," but it's still pretty rough stuff for the happiest hero of the Justice League. Compared to some of Flash's other work, however, killing is a mercy.
So snapping someone's neck is bad but it's, objectively speaking, much nicer than, dunno, freezing them forever in sentient terror to experience eternity in unblinking horror. Which is what the Flash did to Thaddeus Thawne, a literal teenager from the future.
See, Thaddeus, or Inertia, came back from the future to basically be a little dick. He's a clone of Bart Allen (aka Impulse, aka Kid Flash's Kid Flash), but with some DNA from Zoom (aka Eobard Thawne, aka you get it) mixed in. After awhile of being a regular villain -- stealing stuff! punching people! -- he put his grand plan into action, one that ended with Inertia stealing Impulse's speed and allowing a bunch of supervillains to gun Bart Allen down.
When the Flash found out what happened to his kid sidekick, he did not take it easy. He ripped Inertia off the ground, and stole his Speed Force powers so hard that Inertia finally lived up to his name -- and couldn't move or do anything, except for breathe and think.
Yes, the funnest hero got so pissed off he pulled a "I Have No Mouth, and I Must Scream" on a literal (future) teenager. But, just making him immobile wasn't enough. The Flash stuck Inertia in a museum dedicated to how great Bart Allen is, to rub in how much of a failure Inertia is, and how he'll never be anything but a clone. And then the Flash left him there, forever.
Some of you might be thinking that Bart's a villain and The Flash didn't technically kill him, right? But we're talking about an immortal statue that is experiencing eternity wide awake while time moves thousands of times slower than the rest of humanity. In Flash's defense, Inertia did kinda suck, but wow.
But at least that time, the Flash was only ruining the life of a "villain." Because another time he ruined the life of the whole planet, and the best solution he found in that situation? Killing his mom.
A high-stakes event series, Flashpoint begins with the Flash waking up in a brand-new world that is literally ripping itself apart -- Wonder Woman and Aquaman are in the midst of a war that threatens to destroy everything; a powerless Superman is locked in a base; and this is a world where Bruce Wayne is dead and his father has taken up the mantle of Batman while ruthlessly slaughtering criminals. Amidst all this danger and horror, the Flash realizes... it's all his fault.
This nightmare universe was caused after the Flash ran back in time to stop his mom from dying. See, originally the Flash's mom lived until Barry Allen was an older man, but Zoom (aka Neck McSnappington) changed time, killing Barry's mom. So, Barry runs back in time to save her, and in doing so destroys the entire world. Even Wayne Manor is in ruins.
Now, to be fair, the Flash does quickly realize that he needs to fix this, but his idea for a patch job is pretty terrible: Let his mom die. Not make it appear like his mom died. Not create a speed mirage in her shape. No cool superhero save move here. No, his plan -- after destroying the world to save her -- is to let his mom die, shrug and then move on (thus allowing the world to change once more).
After Flashpoint, we got the New 52 (which honestly, one could argue, is the worst thing that Barry Allen ever did, to anyone) where heroes were younger, the world was colder, and almost all of their past adventures were forgotten or erased. Oh, and Flash's mom was still dead. But, that -- at least -- was the worst thing you could say this new Barry Allen had done.
Rebirth was a comic so complicated you'd need an entire article just to unpack it. The world gets reset (again), Watchmen characters show up, there are three Jokers, it's... it's a lot. But, the most important thing that Rebirth did was show that the old, pre-New 52 stories did happen, and that someone was messing with time.
Barry Allen was the first person to begin remembering the old timeline, including how he and his on-again, off-again friend Iris West were married, with children. Naturally, at that point, the Flash told almost everyone he could, letting them know that their lives weren't what they remembered and some dark force was manipulating -- Ha, JK. He told Batman. And that's it.
But don't worry! He did use his older memories to begin creeping on Iris West. He didn't tell her the truth, not about him being the Flash or about their old life together, but he did use all of those memories to Groundhog Day style manipulate her into liking him.
Eventually, though, after literally thirty issues of the comic (over a real world year had passed), The Flash finally told Iris West the... Oh, no, he didn't? Zoom did? Zoom kidnapped Barry Allen and told him that every bad thing that ever happened to him was his own fault and that he, Barry Allen, is actually the true villain of the story? Well, yeah, okay, that's true.
Unfortunately, Zoom is killed by Iris West right before the Flash can snap his neck again.
Two Zoom-murderers head home to their present where Iris realizes what a horrifying skeezoid Barry Allen actually is. But of course, because he's the Flash, he still figures out how to make it worse.
After getting back from the now Zoom-less future, the Flash found out that, during his battle, he received some of the Negative Speed Force, a power that -- Okay, look, short version is he's now darker and his lightning is black and running destroys EVERYthing.
Now, whenever he moves at super speed -- something the Flash does almost every waking moment -- he leaves behind a huge path of destruction, looking like a tornado set down as a bomb went off. A BombNado, if you will.
And most people at that point would do the rational thing -- stop using their powers! (and then sell their life rights to SyFy).
But the Flash? Nah, he keeps using his powers to do stuff like stop diamond thieves and... also just generally run around. It's not unlike the time Peter Parker found himself with loads of extra power when he first donned the symbiote suit. But, again, every time Flash uses his powers it is the equivalent of a mass disaster hitting Central City. Now, to be fair, at one point the Flash does think about, ya know, stopping. But he doesn't do more than think about it.
At a certain point, if you've got black lightning and you've lied to and/or murdered everyone you know, maybe just lean into the thing and become a villain.
If you watched the third season of The Flash, you might be a bit familiar with this story -- Flash turns evil in the future, kills a bunch of people, and then comes back in time to kill... himself... in order to save himself? It's doesn't make a huge amount of sense, but hey, at least Grant Gustin's cute. The comic also doesn't make a ton of sense, but in a different way.
The big connection between the two plotlines boils down to "Evil Flash wants to kill himself, but his past self, and also his lightning looks weird now."
In the comic, one of the last stories that happened in the New 52 before Rebirth came about, Future Flash (Barry Allen, about twenty years in the future) comes back to the past to "heal the Speed Force" by killing his younger self.
This is also, beeteedubs, after Future Flash killed all of his villains in the future. What is it with every hero turning into a villain in the future? Is one huge reference to that Harvey Dent line in The Dark Knight?
Somehow, Barry is upset about this mass murderer coming back, presumably because Barry is no longer the most evil speedster around. That and Future Flash's costume is cuter. Oh, and all the attempted murder/suicide. In the end, the Future Flash throws the older Barry Allen into the future and takes his place before, sadly, the other murderous master racer returns to defeat him.
The CW show has a cooler ending for this super sociopathic speedster where, given the chance to bond with all of his old friends and family, he instead decides, "Fuck it" and tries to spread himself throughout all of time to become a God.
Is this the same channel that used to air Dawson's Creek?
Now, to be clear, in both cases nothing too traumatic had happened to him -- in one version, this was the Flash's reaction to his friends being a little weirded out. Can you imagine what Flash would do if his actions had consequences?