Even The Jokerhimself may not have started out as a bad person. Alan Moore's The Killing Joke shows how losing your pregnant wife and getting disfigured on the same damned day can turn even a decent human being into a mass-murdering maniac. Bear in mind, however, that the Joker later admits he remembers his "bad day" differently from day to day.
"All it takes is one bad day to reduce the sanest man alive to lunacy. That's how far the world is from where I am. Just one bad day. You had a bad day once. Am I right? I know I am. I can tell. You had a bad day and everything changed."
Post-Crisis Tim Drake, Robin III, was hit with an extreme angst upgrade. His mother was killed, then a couple years later his girlfriend was apparently killed and his father, stepmother, and both best friends and a number of his other friends were killed within a period of two months. He was adopted by Bruce to be greeted by two brothers making multiple attempts on his life. He blamed himself for the deaths of several innocent bystanders. After Dick fired him as Robin to replace him with his unrepentantly homicidal little brother he cut himself off from any healthy emotional support. Tim, as Red Robin, left Gotham City in search of the supposedly deceased Bruce Wayne while his old allies were worried for his sanity, due to his gradually declining composure. While it looked like he was about to become a Fallen Hero he determinedly kept himself from taking that plunge.
If you want Batfamily-related mass amounts of trauma, look no further than the series of events that turned Jason Todd, Robin II, into Red Hood. First, there are his last days as Robin, where after the Felipe Garzonas incident, which involved him being unable to stop a woman from committing suicide and then him potentially shoving her rapist off a roof, Jason gets forcibly benched as Robin for his anger over not knowing his parents affecting his crime-fighting, before he finally finds his actual birth mother, and seeks to go to Ethiopia with Batman to meet her. He subsequently sees her captured by The Joker and goes in alone against Batman's orders to try and save her due to his understandable worry about leaving his mom alone with the Joker. Then, it's revealed that Shiela is a drug dealer who has sold Jason out to Joker to cover her tracks, standing there and smoking a cigarette as Joker brutally beats Jason bloody with a crowbar as the poor kid cries for help. Then, to top it off, Joker ties up Shiela and rigs a bomb to explode the warehouse both Jason and Shiela are in, subsequently killing them both right after Shiela discovers the door is locked, dashing any hopes of escape. This is not the end, however, as Jason is later revived due to Superboy-Prime punching reality apart, has to dig his way out of his own grave with a belt buckle and his bare hands, and is immediately hit by a car, giving him severe brain damage which causes him to wander Gotham's streets for months as a homeless kid relying on his Robin muscle memory. Then, the League of Assassins find Jason, who they recognize as Robin, kidnap him off the streets, and dunk him in a Lazarus Pit to heal his brain before showing him that he was completely and utterly replaced as Robin and his murderer is still alive and doing equally heinous crimes, with Batman having seemingly done nothing to permanently stop him or avenge Jason's death. It's not a big surprise when Jason immediately begins training to go on a murder spree after this, and by the end of the Under The Hood storyline, Bruce slashing Jason's throat with a Batarang and leaving him in an exploding building to save the Joker just feels like par for the course for the life of Jason Todd.
Batman has lost sidekicks and allies, and has had multiple efforts to try to make something out of his life crushed. But he's still the same person he was at the beginning of his Darker and Edgier remake as he is now.
Not only is Krypton destroyed but Supergirl survives on Argo City but then it's destroyed. So she's orphaned twice inmostcontinuities.
In Post-Crisis continuity her parents survived Krypton and Argo City's destruction only to die on New Krypton. Which was subsequently destroyed. In other words, she has lost her home planet three times.
Kara becoming a Red Lantern in Red Daughter of Krypton is the result of one: In Last Daughter of Krypton, she wakes up with missing memories, on an alien world, all alone. She is promptly attacked by men in Powered Armour. Shortly after that, she encounters a grown man claiming to be her baby cousin. Shortly after that she's lured in and kidnapped by an amoral trillionaire who wants the secrets of Kryptonian technology, poisoned with Kryptonite, and then the guy who rescues her is murdered in cold blood. After she gets away from all of that, she's utterly alone in an alien world, then finds a link to her very dead home. She follows it... and finds that her home is basically a ghost city, whereupon she is beaten up by a Kryptonian supersoldier called a Worldkiller. After escaping all that, she has to fight four Worldkillers, then, exhausted, is promptly attacked by the US Army and Police, with only one human standing up for her (and is, conveniently, an Omniglot). Said human befriends her, then turns out to be the Silver Banshee, who is being hunted down by her father, the Black Banshee. After briefly being absorbed, body and soul, she fights her way out. Then she gets attacked again, while on a date. Oh, and the first man she falls in love with is H'el, who's manipulating her, using her affection for him to trick her into a brief Face–Heel Turn. Then, in defeating H'el, she's poisoned with Kryptonite. Again. And then there's the revelation that her father was experimenting on her. And then she ran into Lobo, who taunted her until she blew up.
The Final Days of Superman: Being exposed to the fire pits of Apokolips, a vault full of Kryptonite and Rao's energy has caused permanent cellular damage to Superman, which eventually killed him. In the end, the last few months of Post-Flashpoint Superman's life were one prolonged string of misfortunes that saw a tragic end.
The 90s were a bad time for Aquaman with all the stuff that happened to him there. His infant son was murdered by Black Manta, and not only does his wife Mera blame him and his "weak genes" for their son's death, but she goes insane and has to be committed to an asylum. Oh, and Aquaman has his telepathy stolen and his hand eaten by piranhas. Not to mention nearly having his place as ruler of the seas almost stolen by the corrupt god Triton. And people wonder why Aquaman was so angry at this time in his life.
Aquaman (1991) puts Arthur through the wringer, with a lot of it exacerbated by his self-loathing. First Poseidonis is attacked by the surface, then by sharks, then by well-intentioned invaders from Tritonis. When Aquaman goes to the surface to try and make peace, Black Manta allied with not-so-well-intentioned Tritonians and attacks him, blowing up Arthur Jr.'s grave to get a rise out of him. After a brutal fight where both men almost die, Arthur is then attacked in the mental plane by his evil mirror-self, Thanatos, in an attempt to take control of the body. After all that, plus not stopping to rest even once, Arthur is finally able to relax and heal a little.
Roy Harper, the former sidekick of Green Arrow, has had it pretty rough recently. In Cry for Justice he got his arm chopped off by Prometheus. Then Prometheus and his accomplice the Electrocutioner unleashed a Kill Sat on Star City, killing thousands including Roy's young daughter Lian. This drove him back to drug abuse, which just made things worse. To add insult to injury, when he and Cheshire got involved, he couldn't perform, so to speak. He became a Jerkass, railing against his former friends and teammates, going so far as to blame Mia for Lian's death and calling Donna a whore when she tried to sympathize with him. Later he agreed to join Deathstroke's Titans (a team of assassins for hire), though this is because he is emotionally blackmailed into joining the team by Cheshire so they can kill Deathstroke. And then, he finds out Deathstroke had secretly gotten him addicted to an even worse drug, Bliss, which is literally made from human children. Thankfully, the end of that volume of Titans had Roy stopping Deathstroke and reclaiming the Titans name. And it wasn't until Convergence when it was shown that Roy had successfully managed to beat his addiction on his own, reconciled with his friends, and regained a semblance of peace leading into Lian being brought back to life. Unfortunately, this was all undone thanks to the New 52 and Rebirth, where Roy's history was greatly corrupted thanks to Barry Allen and Doctor Manhattan destroying the DCU. All of Roy's friendships and personal connections were destroyed, Lian was literally erased from existence, and he was reduced to being a glorified lackey to Red Hood.
In The Trial of the Flash, the Rogues' Gallery and corrupt lawyer N.D. Redik make the Flash's life miserable. Redik arranges for Flash's lawyers to be killed, and while they're rescued, he's very shaken up by it, and the Pied Piper mind controls the mayor and innocent civilians to hate the Flash.
