Shonen anime is arguably the most popular demographic of anime, as it appeals to many more fans than its intended core audience of teenage boys. Shonen anime often has compelling and diverse characters that any viewer can root for or identify with, and these stories have universal and timeless themes of courage, hope, the power of friendship and belief in oneself.
Shonen protagonists like Son Goku and Uzumaki Naruto embody these themes well, but these heroes have their dark side too, and perhaps they are scarred by a tragic death, discrimination, unresolved grudges or more. Some anime fans put heads together to figure out which shonen hero would be scariest if they became a supervillain, and there are a handful of strong contenders for the scariest hero-turned-villain of them all in terms of power, aesthetics and attitude.
Son Goku, The Saiyan Superman Turned Evil
Son Goku, the iconic Saiyan hero of Dragon Ball, is often compared to DC's Superman for being a powerful melee alien who defends his adopted homeworld of Earth from all manner of threats. Goku is beloved for being a "himbo" -- a goofy but well-meaning fellow who gets the job done despite his many antics.
Goku is usually cheerful and optimistic as a hero, but he can also become frighteningly angry when his beloved friends or family are threatened, and he may show no mercy to the most despicable villains in the Dragon Ball universe. He has shown his dark side before, but ultimately, Goku is too difficult to imagine as a scary villain, even if he somehow intended to do evil. It's difficult to corrupt a cheery and fun-loving person like him.
Uzumaki Naruto Has An Inner Monster
Uzumaki Naruto was born with a monster inside him -- the nine-tailed fox Kurama. His mother Kushina once contained Kurama inside herself as part of her clan's theme of sealing jutsu, and now it's Naruto's turn. Unlike his mother before him, Naruto didn't have the benefit of people who understood him and the burden he bore -- in fact, the townsfolk deeply resented him for being the embodiment of the fox that nearly destroyed the village.
Naruto was inspired to become the new Hokage to prove himself to all the villagers, and he succeeded, but he cannot deny the darkness inside him forever. He is scarred by widespread fear and ostracization, and he's also quick to anger. When riled, he may manifest one or more of Kurama's tails in a dense biju cloak and go wild like an animal. He will even resemble a fox as more and more tails appear, and everyone who sees this is paralyzed with terror.
Kurosaki Ichigo Houses A Dark Spirit, Too
Kurosaki Ichigo is one of the three "main" shonen heroes of the 2000s along with Naruto and Luffy, and he has the most villainous attitude of the three. He's a punkish antihero with no heroic ideals beyond protecting his friends, and like Naruto, he also has an inner monster.
In this case, he must contend with his inner Hollow, a sadistic and feral being that manifests as a skull-like mask with red lines on it, and Ichigo might lose control of himself. If he's pushed to the brink, such as during his fight with Ulquiorra, his Hollow form is pushed to the next level, complete with two huge horns, a brutal fighting style and the use of cero blasts, like a true Hollow.
Itadori Yuji Is Ryomen Sukuna's Vessel
Itadori Yuji is yet another shonen hero with an "inner monster," and that's what puts him in the running for scariest shonen hero gone bad. Jujutsu Kaisen, a hit shonen series inspired by Bleach, is a dark and scary story of negative human emotions manifesting as monstrous curses, and jujutsu sorcerers risk their lives to fight these supernatural threats with their own curse energy.
Yuji is normally a cheerful and friendly fellow, but he also houses Ryomen Sukuna, the dreaded king of curses, and sometimes, Sukuna takes over Yuji's body and might refuse to give it back. If Yuji turns evil, it's because he ate more fingers than he was ready for and allowed Sukuna to take over for good.
The Scariest Shonen Hero Turned Evil: Uzumaki Naruto
The "inner monster" concept helps make many shonen heroes scary, and some seinen heroes are like that too, such as the half-ghoul Kaneki Ken and Eren Yeager. However, among all shonen heroes, Uzumaki Naruto stands as the scariest one in terms of raw power and aesthetics alike. In fact, this is why the Hidden Leaf Villagers rejected him to begin with. Naruto's fox chakra is powerful, alien and intense, and his feral attitude and reckless ways would make him even scarier if he turned evil somehow, especially in Shippuden. He's a true monster.
