Typically, anime villains are presented as having few to no redeeming qualities. By the time that the protagonist confronts them, they are so invested in their evil that it has become a significant part of their entire personalities.
However, there have been many instances where villains are victims of circumstance. A single bad day changed their entire lives for the worse, putting them on a trajectory of complete malevolence. Through identifying these antagonists and the terrible fates that befell them, it becomes easier to gauge whether or not their backstories are sympathetic and rationalize their actions.
This article contains spoilers from the Attack on Titan manga.
10 Eren Was Destined To Fall From The Beginning (Attack On Titan)
In the beginning of the series, Eren was forced to watch his mother get devoured by a pure titan. At first, he thought that titans were responsible and vowed to exterminate all of them.
However, he later learned of Marleyan involvement and redirected his rage to the rest of humanity. Considering that an older Eren deliberately arranged for his own mother's demise, he created the circumstances necessary to motivate his hatred. Without that single fateful day, his future would have been much different, and Paradis may not have collapsed.
9 Everything Changed After Obito Got Crushed (Naruto)
During a particularly eventful shinobi mission, Obito was pinned beneath a huge boulder and left for dead. In a final act of sacrifice, he gave Kakashi one of his sharingan before presumably passing away. However, Obito never actually died.
He was rescued and restored by Madara Uchiha, who strengthened him using Hashirama cells. The man's motives were not benevolent; instead, he manipulated Obito into becoming his servant and portraying the outside world as if it were irredeemable. After Madara's death, Obito acted on his behalf and was ultimately responsible for his resurrection through the Edo Tensei.
8 Sho Disappeared After His Mother's Death (Fire Force)
Sho was an incredibly powerful White-Clad soldier and a pillar that the Evangelist needed for a second global attack. Desperately committed to the cause, he ignored most of Shinra's sentiments during their first clash. Unfortunately, Sho is a victim of circumstance.
His mother's death and destruction of his home took a heavy mental price and rendered him malleable to the cult's suggestion. By the time Shinra actually found him, the villains had indoctrinated Sho so badly that it was almost impossible for him to leave. When he tried, Haumea used her Ignition Ability to guarantee his loyalty.
7 Scar's Life Was Changed Due To Amestris' Attacks (Fullmetal Alchemist)
Scar was an Ishvallan forced to endure the horrors of war. Amestris' nation of alchemists proved too much for his country to handle and resulted in his brother's death.
Before passing, his brother gave him his hand, which allowed him to rebuild things as efficiently as he could destroy them. This gift only inflamed Scar's rage and compelled him to hunt down Amestris' soldiers like animals. Before joining forces with the Elric brothers, he was a domestic terrorist who caused widespread anarchy.
6 Everything Changed After Shigaraki Killed His Own Family (My Hero Academia)
As a child, Shigaraki had aspirations to become a hero. These dreams were quickly staunched by his father, who constantly berated and belittled him. Eventually, this abuse came to a head when Shigaraki's Quirk first manifested. He accidentally used his "Decay" Quirk and killed his entire family.
Horrified and alone, Shigaraki wandered the streets until coming across All For One. The man happily adopted him, grooming him to become a successor much like All Might did for Izuku Midoriya. Shigaraki took his master's lessons in stride and promised to destroy hero society.
5 Doflamingo Lost Everything Due To His Father (One Piece)
Dissatisfied with the privilege and cruelty of Celestial Dragon life, Donquixote Homing denounced his status and took his family to live with ordinary people. Predictably, they resented his origins and strung up his family in the street.
If Doflamingo didn't use his conqueror's haki for the first time, he likely would have died before reaching puberty. Enraged at his father's decision, he executed him in front of his brother, Corazon. Ever since, Doflamingo has walked down a dark path and become one of the high seas' most feared men.
4 The Millennium Ring Corrupted Bakura (Yu-Gi-Oh!)
At first, Bakura presented himself as a bright and relatively gullible young man. However, that changed upon discovering the Millennium Ring and its dark host. Like Yugi, Bakura was possessed by a second and completely new spirit.
This entity was far more malevolent and had a personal vendetta against the Pharaoh. As a result, Bakura became an enemy of Yugi and his friends without even realizing it. Worse yet, his attempts to get rid of the ring all mysteriously ended in failure.
3 Rui's Encounter With Muzan Ruined His Life (Demon Slayer)
Rui was once a frail young boy whose condition prevented him from playing with others. It was so inhibiting that he could not even walk or leave his room. Desperate to socialize, he made a deal with Muzan to gain the strength he wanted.
However, he failed to anticipate the steep toll it would take on his humanity. Ostracized from his home, Rui hoped to create a new "family" by abducting strangers and forcibly converting them into demons. In this regard, their fates were even more tragic than his own since they never had a real choice.
2 Hendrickson's Actions Were Influenced By Fraudrin (Seven Deadly Sins)
After a deadly encounter with Fraudrin, Hendrickson was possessed and became his vessel. This granted the demon an unshakable grip on Britannia and allowed him to turn its subjects against the Seven Deadly Sins.
Hendrickson could only watch as his body was forcibly manipulated toward evil purposes. He was exceedingly grateful once Meliodas freed him from corruption and promised to redeem himself however possible. Nonetheless, based on his interactions with Ludociel, he is still highly idealistic and easy to manipulate.
1 Nagato's World Crumbled After Yahiko's Death (Naruto)
Realizing that the Akatsuki posed a threat to their plans, Danzo and Hanzo the Salamander joined forces. They cornered Nagato, Konan, and Yahiko, forcing the former to choose between the latter two. Understandably, Nagato was not keen on playing with his friends' lives, so Yahiko killed himself for Nagato's sake.
This completely shattered Nagato's perception of reality and gave rise to the more commonly known and villainous version of the Akatsuki that debuted in the series. In a single night, Jiraiya's teachings were completely undone, and a monster was created.