Shonen anime is generally written with teenage boys in mind, with classic examples ranging from Dragon Ball to Naruto to Demon Slayer, among others. These anime can be remarkably deep and complex, considering their intended audience, but shonen has its limits while seinen anime does not.
Seinen anime doesn’t have to be dark, violent, or totally serious, but it can be, and seinen has near-unlimited potential for thematically and emotionally deep and complex content. This means that some shonen anime villains are wasted in shonen anime, and those villains could be more thoroughly fleshed out if they had been written into seinen anime instead.
10 Tomura Shigaraki (My Hero Academia)
My Hero Academia is a shonen anime, so it has many characters and often depicts them in numerous Quirk-based battles all throughout the anime. The villains have some serious depth to them, such as commentary on societal norms and good vs evil, but seinen anime could take it further.
Tomura Shigaraki could have been the primary villain of a seinen superhero deconstruction anime, and he would have even more complex and thought-provoking depth to him. He would feel more like a Tokyo Ghoul character in that case, and it would make him all the more memorable.
9 Ulquiorra Schiffer (Bleach)
Bleach has a large variety of villains, some of whom are much deeper and more serious than others. A clear standout is the aloof, stern Ulquiorra Schiffer, the 4th Espada, who served as Sosuke Aizen’s nihilistic right-hand man in the Arrancar saga.
In a seinen anime, Ulquiorra could have been the major focus, and his dark, empty worldview could have been fleshed out as deeply as the author wished. Ulquiorra’s attitude and worldview would challenge Ichigo and his friend Orihime on a philosophical level, too, and disturb them greatly.
8 The Six Paths Of Pain (Naruto)
With his visual design and jutsu, the villainous Pain is obviously a shonen character, but he could have been designed a bit differently for a seinen take on Naruto. In that case, Pain could have been the main villain, and his worldly themes of hatred and revenge would resonate all the more.
Author Masashi Kishimoto could have dived as deeply as he liked into this theme, and Pain would dominate a seinen version of Naruto where ninjas are as grim, dangerous, and scary as pop culture suggests they should be. A seinen Pain would drive the point home that there are no clear or easy answers regarding the cycle of hatred and violence.
7 Katana Man (Chainsaw Man)
Chainsaw Man is one of several shonen anime that blurs the line between shonen and seinen as a partial deconstruction of all things shonen. Many characters and scenes in Chainsaw Man feel half-seinen already, including the vicious antagonist called Katana Man.
Katana Man is a vengeful man with the power of swords, hence his nickname, and he’s determined to avenge his mobster father and kill Denji. He’s the perfect character for a grim seinen crime thriller with supernatural elements, like a Tarantino movie with devil contracts.
6 Muzan Kibutsuji (Demon Slayer)
Most of Demon Slayer’s characters are flamboyantly shonen in design, from the terrified dandere Zenitsu to the lively Kyojuro Rengoku and the combat-loving thug Akaza. An exception is Muzan Kibutsuji, the king of all demons who has business with the Kamado family.
Muzan is a merciless, brutal villain who blends right into human society and will kill without remorse, all for his own selfish goals. He would make a fine seinen villain, exploring the hair-raising depths of depravity while sending flesh-eating monsters after the hero every night.
5 Mahito (Jujutsu Kaisen)
Jujutsu Kaisen is another dark shonen anime that feels rather seinen at times. The anime balances its darkness with wacky humor from Satoru Gojo and his students Yuji and Nobara, and the action definitely feels more shonen than seinen.
That said, the antagonist Mahito would do well in a seinen anime due to his horrifying worldviews. He thinks curses are superior and humans deserve to be wiped out, and in a proper seinen anime, Mahito could go into much more depth on that topic and explain why humanity really does deserve to perish.
4 Mello (Death Note)
The supernatural crime thriller Death Note is ultimately a shonen anime, but it actually has serious appeal for seinen fans too, with its complex themes of justice and morality and its hardboiled police character Soichiro Yagami.
The super-detective L feels pretty shonen, but one of his successors, Mello, would do well in seinen. In a seinen take on Death Note, Mello would dominate the narrative with his criminal antics and his brutal, self-centered scheme to seize the notebook and become a truly unstoppable crime lord.
3 Gori Suido (Tokyo 24th Ward)
Mayor Gori Suido was an antagonist in the cyberpunk anime Tokyo 24th Ward, but he was never a true villain. Instead, he just went too far trying to do what he thought was right and created a state surveillance system using his daughter’s comatose body as its living data processor.
Gori Suido later regretted his actions and was redeemed, but Tokyo 24th Ward could have done more. A truly dark, cyberpunk seinen version would make Gori Suido more like a Ghost in the Shell villain and have him thoroughly explore transhumanist themes about where humanity ends and machinery begins.
2 Biscas T. Balmus (The Rising Of The Shield Hero)
The Rising of the Shield Hero is a fairly standard isekai shonen anime, but some of its characters are pretty dark and would make more sense in a seinen anime. Even protagonist Naofumi Iwatani could be remade into a gritty seinen antihero, and among the villains, Biscas T. Balmus would do well in seinen, too.
Biscas T. Balmus was a high priest of the Church of the Three Heroes, and he and the four Cardinal Heroes eventually came to blows. In a seinen fantasy anime, though, Biscas could have represented deeper themes of the abuse of religious power and made life truly a living hell for Naofumi and his allies, sort of like Father Mozgus in Berserk.
1 Wrath/King Bradley (Fullmetal Alchemist: Brotherhood)
The popular shonen anime Fullmetal Alchemist: Brotherhood has the thematic depth of any good seinen anime, though its humor and action scenes clearly mark it as true shonen. Still, some FMA villains could feature prominently in a seinen version of this franchise.
The best example is the sword-slinging Wrath, a vicious and merciless antagonist who never had any control over his own life. He could embody all kinds of themes about war, vengeance, and more in any seinen version of FMA.
