The most popular shonen action anime titles may vary greatly in style and lore, but they all share some fundamentals, such as the need for a "starter" villain. Most shonen and seinen action series begin with a starter villain, introducing the protagonist and viewers to the world's combat system, and those first fights are usually a point of no return for the protagonist.
The original "big three" shonen villains were the Hollow known as Fishbone D, Higuma (chronologically), and the rogue ninja Mizuki. Demon Slayer, Jujutsu Kaisen, and My Hero Academia can now be compared to their starter villains to determine whether Tanjiro, Yuji, or Izuku had the best, scariest, and most meaningful first foe.
Katsuki Bakugo Was Almost Murdered by the Sludge Villain
My Hero Academia features some of modern shonen's best villains in terms of their character designs, Quirks and even philosophies about subjective justice and societal inequality. Still, it all had to start somewhere, with the unnamed sludge villain being protagonist Izuku Midoriya's first true enemy. The sludge villain was a fairly typical petty criminal who burst onto the scene during a bank robbery, and by chance, he seized Izuku's childhood friend Katsuki Bakugo as a hostage on the streets. Izuku watched in horror until he charged in to prove he was a real hero despite being Quirkless, but it took All Might's intervention to defeat the sludge villain and save the day. Thematically, the sludge villain represented how common and bizarre some criminals in this world can be, and he served as an opportunity for Izuku to show All Might his heroic heart in the face of mortal danger.
Nezuko Kamado Betrayed Her Own Brother
Demon Slayer's first episode, "Cruelty," indirectly introduced the supervillain Muzan Kibutsuji, who slaughtered the Kamado family off-screen and turned Tanjiro's little sister Nezuko into a demon. Tanjiro returned home from a coal-selling errand to find his family dead aside from Nezuko -- and then Nezuko turned on him. She couldn't control her demonic hunger, and she tried to sink her fangs into her brother until Tanjiro fought her off with an ax. Then Giyu Tomioka the water Hashira arrived, and Tanjiro desperately fought to shield Nezuko from him despite the danger. Impressed, Giyu agreed to spare Nezuko, who fortunately calmed down, ending the tragic fight before any blood was shed.
The Harsh Introduction to Curses by Yuji Itadori
Jujutsu Kaisen protagonist Yuji Itadori is like a nicer Ichigo Kurosaki -- a tough and cool high school boy whose life was turned upside down when monstrous, supernatural creatures arrived in force. One night, a powerful curse went on a rampage in Yuji's school, and Yuji and his classmates were helpless until Megumi Fushiguro the sorcerer arrived to help. Then, when all seemed lost, Yuji swallowed one of Ryomen Sukuna's severed fingers and gained immense curse power, allowing him to break free of the monstrous curse's grip. That plot twist allowed Yuji to finish the fight in Episode 2, when Satoru Gojo himself showed up to witness the battle's conclusion.
The Curse, The Sludge Villain & Nezuko Kamado: Who's The Best Starter Villain?
Whether Tanjiro, Izuku, and Yuji liked it or not, all three of the initial villains were evil creatures that posed a threat to the hero. Nezuko Kamado, though, stands out as the most interesting and unforgettable of them all. The fact that the other two villains don't even have well-known names supports the idea that Nezuko Kamado is a legitimate character whereas the first curse and the sludge villain were merely plot devices to introduce the story.
Nezuko is no ordinary demon; she is Tanjiro's little sister and the only other survivor of the Kamado massacre, giving Tanjiro immense personal stakes in their brief fight. Nezuko wasn't just fighting her brother and Giyu; she also fought her own demonic hunger and nature, and eventually, Nezuko triumphed over them. Tanjiro, meanwhile, showed incredible courage and resolve by fending off his demonic sister while refusing to harm her or allow Giyu to finish her off.
Nezuko was both a monster and a victim, and her new demonic status was the catalyst for Tanjiro's personal quest to save her humanity. Tanjiro would have to prove to others, such as the wind Hashira Sanemi, that Nezuko is not a villain or a monster, which makes her a far more effective shonen antagonist than the sludge villain or first curse could ever be.