Whether they were good from the outset or they came around to the idea after a few years, there are few characters in the DC Comics universe who have a happy backstory. The company’s heroes were often pushed into greatness by the unhappiness they faced in their everyday lives. Characters like Batman and Rorschach from Watchmen have both experienced great losses and see lawbreaking everywhere they look and no one doing anything about it. Rather than call 911 and wait for the police, they put on costumes and take matters into their own hands.
On the flip side of that coin, anti-heroes like Harley Quinn are happy to live a life of chaos until it all falls apart around them, and their grim backstories make it even harder for these former villains to turn their lives around. While the backstory of many of these characters comes from witnessing a close personal tragedy, some of them were simply twisted until they popped and had no other choice than to adopt the life of a masked hero.
He may be a fun guy to have around at parties, but Beast Boy has had to overcome some serious personal issues. While he grew up traveling with his scientist parents, life wasn't all roses for the young Garfield Logan. His parents were abusive, something that pushed him inward as they grew colder.
After he was infected with a deadly virus while in Africa, Beast Boy's father injected him with a serum made from the DNA of a green monkey. On one hand, he wanted to save his son's life, but on the other, he was testing an experimental substance and using his sick son as a guinea pig. The serum saved his life but turned him into a changeling covered in green fur.
Beast Boy continues to have a love/hate relationship with his parents even after their passing, mostly because he thinks he could have saved them from a gruesome end.
After being beset by an inter-dimensional gelatinous creature in his parent's laboratory, Vic Stone was left clinging to life with little of his original body left. Rather than let him pass, Stone's father fitted his son with an experimental robotic body. When Stone came to, he realized that he was now more prosthetic than human and told his father that he would have rather perished than be turned into an experiment.
Cyborg's creation harkens back to the fear of science present in the 1950s and the Victorian era. He's presented as both a Frankenstein's Monster and the proof that, with the right tools, a person can turn themselves into a god. Thankfully, Cyborg chooses to join up with the good guys.
It's one thing to realize you're the last of your race, like Superman, but for Martian Manhunter, the finality of his existence is so much more tactile. After his twin brother was convicted of a horrific act and forced to have his mind wiped and his telepathic powers removed, he created the "Hronmeer's Curse," a disease that cause Martians to spontaneously combust the moment they use telepathy.
Unable to stop his brother, Martian Manhunter is forced to watch his friends, family, and species perish in front of him. It isn't until he's accidentally brought to Earth that he is able to push beyond the pain of his past and start working with the Justice League to defend humanity.
Swamp Thing's origin is fitting for his terrifying frame. Like the Universal Monsters before him, his creation lies in the hubris of science and the sick ironies of life. There have been a few different Swamp Things over the course of history, but the most prominent is Alex Holland, a scientist who was working in a secret lab under the swamps of Louisiana.
After he and his lab are blown to kingdom come by thugs, Holland is doused in chemicals that put his memories into the surrounding plants. When the undergrowth of the swamp coalesces into a humanoid, it believes itself to be Holland when, in fact, it's just living with his memories and emotions.