In the world of anime, mega-popular villains can catapult a series into stardom, especially in the world of shonen and seinen. Many of these villains are tragic and sympathetic, while others are downright vile and are wicked to the very end. Yet other villains end up becoming heroes themselves, taking everyone by surprise.
Some of these anime villains were actually heroes all along and the protagonist simply crossed them when they first met, or the "villain" had to act that way while under orders. In other cases, the villain began as a rogue of sorts, and joined the heroes' team after having a change of heart. Some anime villains prove that there is a shred of good in even the most wicked of foes.
10 Itachi Uchiha, The Clan Slayer (Naruto)
Itachi Uchiha is a classic example of an antagonist who was actually a hero along, but was forced to operate like a villain due to various circumstances. Itachi and his younger brother Sasuke got along well in their youth, but Itachi had a mission that put the entire Leaf Village at risk.
The Uchiha clan was going to rebel and act out in hate, so Itachi was ordered to slaughter the Uchihas and prevent disaster. Itachi spared Sasuke, though, and years later, Sasuke learned the truth— and decided for himself what to do about it.
9 Askeladd, The Bitter Viking (Vinland Saga)
Early in this medieval anime, the cunning Viking Askeladd lured the mighty Thors into a trap in the Faroe Islands, and dueled him. Thors lost his life due to trickery, and his son Thorfinn swore vengeance, while also acting as a surrogate son for Askeladd. It's complicated.
Askeladd isn't totally evil, however, and he wants to free the Welsh people from the threat of the Vikings. In fact, Askeladd taught Thorfinn many lessons on war, life, death and vengeance, and Thorfinn put all this to good use during his later quest to found the peaceful nation of Vinland.
8 Captain Byakuya Kuchiki, The Law-Abiding Soul Reaper (Bleach)
Captain Byakuya Kuchiki was born into a noble family, and he had to set an example by being a law-abiding, tradition-bound leader of his family and squad 6 alike. He and Ichigo came to blows when the innocent Rukia was slated for execution, but Byakuya never meant any harm. He only wanted to protect the peace.
Fortunately, Byakuya had a change of heart after reaching a stalemate with Ichigo, and he acted on his familial love for Rukia by defending her from Sosuke Aizen when the latter turned traitor. From this point on, Byakuya would be the protective big brother Rukia always wanted.
7 Bruno Bucciarati, The Kind Mobster (JoJo's Bizarre Adventure)
Bruno Bucciarati was first introduced as an antagonist in the Golden Wind story arc, clashing with Giorno Giovanna in an intense Stand battle. But that didn't last long. Bucciarati belonged to the notorious Passione gang, but he was no monster.
Instead, Bucciarati shared Giorno's dream of freeing Italy from the terror and violence of crime families and gangs, and after that initial battle, Bucciarati extended the hand of friendship, and Giorno accepted it. They shared a common goal, and soon got to work achieving it.
6 Laxus Dreyar, The Lightning Dragon Slayer (Fairy Tail)
Laxus Dreyar, the lightning dragon slayer, was introduced as an antagonist after the battle against the Phantom Lord battle. Laxus was determined to weed out the Fairy Tail guild's weakest members, and while this was a bad idea, Laxus really did have the guild's best interests at heart.
Laxus was defeated, and he was exiled from the guild for a time. However, he felt strong bonds to his grandfather (Makarov) and his guildmates, and he would later return as a loyal friend. He soon risked his life for the sake of his guildmates, showing his true colors at last.
5 Scar, The Vengeful Monk (Fullmetal Alchemist: Brotherhood)
Scar, an Ishvalan monk, had vengeance on his mind when the state alchemists wiped out his countrymen in a brutal and senseless civil war. No one could really blame Scar for seeking blood for blood, but Scar's destiny really lay elsewhere.
Scar bore the tattoos of alchemy, and he soon learned to direct this power at Father and his minions, not the state alchemists. He later became Ed's ally and helped take Father and Solf J. Kimblee down, to truly restore peace and balance to the world. Only then can his fallen countrymen rest in peace.
4 Uncle Iroh, The Wise Firebender (Avatar: The Last Airbender)
Uncle Iroh was really only a de facto villain, since he was supporting prince Zuko on his quest, and he was a part of the Fire Nation. However, Iroh was a miniature Avatar in his own right, since he sought balance and harmony with the world, contradicting his conquest-minded younger brother Ozai.
Iroh also realized that all things and all people are connected, and hurting one will end up hurting them all. Iroh sought to end all conflict and reconcile the feuding parties, starting with Zuko, and he achieved that dream. It also helps that he belonged to the White Lotus organization.
3 The Great Holy Knight Dreyfus (The Seven Deadly Sins)
Dreyfus was a great holy knight who happened across the powerful demon Fraudrin one day, alongside his friend Hendrickson. Fraudrin ended up possessing Dreyfus and committed unspeakable acts while using him, and Dreyfus was introduced in the anime as a villain.
Fortunately, Meliodas and his friends put a stop to that, and Fraudrin was slain, freeing Dreyfus. Now, Dreyfus' considerable power can be use for good, as was always intended, and Dreyfus can seek a way to make things right after all Fraudrin has done.
2 Inosuke, The Hard-Headed Slayer (Demon Slayer)
Fortunately for Tanjiro and Zenitsu, Inosuke's tenure as a villain was very short-lived. He was a wild card during the fight against Kyogai, ready and willing to fight any challenger who crossed him. He was eager to fight Nezuko, and he beat up Zenitsu because the latter tried to keep Inosuke away from Nezuko.
Then Inosuke went up against Tanjiro, and a headbutt helped put Inosuke in his place. From that point on, Inosuke tagged along as a rough but loyal ally, using his twin nichirin blades to challenge demons of all shapes and sizes. He was always a demon slayer, but his personality borders on villainy.
1 Neji Hyuga, The Bitter Ninja (Naruto)
When Neji Hyuga first appeared, he was a formidable antagonist to both Naruto Uzumaki and Hinata Hyuga, the latter of whom is his cousin. Neji is a bitter determinist who thinks that everyone's fate is set, and he tried to beat this "lesson" into Naruto and Hinata during the Chunin Exams arc.
Neji isn't evil at all. He's just upset by his perceived lot in life, and he simply needs some hope— and a friend or two. Naruto defeated him during their duel, and Neji began to change his tune before long. In fact, he gave his life to protect his comrades much later, near the end of the Shippuden storyline.