Everyone is capable of being good and evil, including shonen anime characters. It's not a massive stretch to see fans consistently arguing in favor of even some of the most heinous actions a character commits either because they like the character in question or because they have some justified reason for why they went to the dark side.
Several characters have gone to the dark side or went into the anti-hero side of the equation. Then some are just plain evil, with no real explanation or more of a self-aggrandizing reason. This article will showcase these types of shonen anime characters, highlighting the good reasons for going dark and the fantastical versions of evil.
This is just the author's opinion. It will also contain spoilers for all the anime discussed. Sho Tucker is excluded for being too obvious a monster.
5 shonen anime characters whose turn to darkness was justified:
1) Crona (Soul Eater)
Crona from the shonen anime Soul Eater has several reasons to be featured here. Medusa Gorgon is not a person fit to be a parent, considering what Crona went through when they were young. Starvation and malnourishment are just a few beats in their repertoire of torture and pain.
Would anyone blame them, even after making friends with kinder people like Maka and Black Star, if they went dark? Being forced to do their mother's bidding after their difficult upbringing didn't help, especially not having to use Black Blood on an entire country.
So, Crona's mind snaps in the manga after Medusa shows false kindness, and they stab Medusa to death and start on the road to becoming a kinshin themselves.
Medusa's plans are eventually foiled as Crona holds the kinshin Asura back in the manga to prevent a complete takeover of their mind and the destruction of the world by sealing them both. In the anime, Maka kills Medusa and Crona is able to escape going completely dark but still going dark after a while.
2) Itachi Uchiha (Naruto)
There was going to be an Uchiha on this list, and they are practically the poster kids for dark turns in the ninja shonen anime Naruto. Though Sasuke had several valid reasons for going dark, it took him a long time to get his head straight. For a more in-depth look, Itachi Uchiha is the subject of this entry.
Being forced into a dark choice is another thing, while willingly submitting is another. Itachi tried every avenue, possible option, and outcome - but everything failed. This was seen through happenings ranging from Shisui being ambushed by Danzo to the Uchiha clan not listening to him.
The Uchiha clan massacre happened as Itachi fled the village, swore the Third Hokage to protect and safeguard Sasuke and laid the groundwork for Sasuke's revenge.
Whether he did so perfectly is another debate entirely, but Itachi was justified in his descent into darkness, and he regretted every step of the way.
3) Scar (Full Metal Alchemist/Brotherhood)
Without mincing words, the former shonen anime villain Scar is a genocide survivor. A serial killer by the time of both the 2003 and Brotherhood adaptations of the shonen anime Fullmetal Alchemist, Scar killed quite a few people in his bloody vengeful campaign against State Alchemists, triggered by the killing of his people and his brother.
Scar is the personification of wrathful grief, a victim of genocide amongst other horrific incidents. He targeted State Alchemists indiscriminately, from major sadists like Kimblee to people that had nothing to do with the genocide of the Ishvalens like the Elric Brothers.
So, it was justified, given the horrible circumstances that birthed his need for revenge.
He would find out the truth, that Homunculi used everything, but it would take a long journey along the Amestrian countryside and beyond.
4) Eren Yeager (Attack on Titan)
Eren Yeager from the shonen anime Attack on Titan wanted to take revenge on the Titans for the death of his mother. When Eren started learning the truth, it undid whatever form of sanity he had left. How else does someone justify the genocidal Rumbling plan that would leave the world mostly barren save for Paradis island?
Naturally, it's more complicated than that. While this shonen anime character's entire being was dedicated to the death wish of fighting Titans, everyone else seemed to be trying to move on.
Eren, however, couldn't or wouldn't and stagnated even as the situation got more complex. The truth, of course, didn't help - the realization of just how messy the Marley and Eldia war was did not matter to him.
.It is not an excuse for attempted genocide, but it's understandable why he wanted to continue the conflict against Marley since they never stopped the cycle of hatred.
5) Dabi (My Hero Academia)
Formerly known as Toya Todoriki, Dabi is the thought-deceased son of Enji Todoroki, aka Endeavor, in the shonen anime My Hero Academia. Being put through the training from the hell-ish Shoto, Toya bore its brunt - coupled with a louse childhood when his father would use him as a tool.
This drove a massive wedge in the family, and the gap only widened after Toya practically immolated himself when Shoto was born. This would later come back to bite the family when Dabi revealed himself over the air and went viral.
The only other thing is that All for One saved him and paid to bring him back to life after three years of being comatose.
Dabi was an abusive victim pushed around by an abusive father - subsequently taking that abuse out on the rest of the world. Shoto and Dabi are fighting to bring that sad story to a close.
5 shonen anime characters who were just evil:
1) Frieza (Dragon Ball Z)
Evil emperor and tyrant of Dragon Ball Z, Frieza is one of the most iconic villains in shonen anime. Whether it's his sadistic personality, him blowing up planets, or otherwise punishing his minions because it was Tuesday or because they failed him, Frieza is quite the monster to behold.
Besides his sadism, Frieza is brilliant, arrogant, and cruel. He's responsible for the deaths of many, including multiple planets, and was the one who kickstarted Dragon Ball as a whole with the destruction of Planet Vegeta.
Add in the Namekian slaughter, the deaths of Vegeta, Dende, Krillin, and others, and his attitude even in Super, and it's easy to see why Frieza made this list.
Even with saving Universe 7 in the Tournament of Power in the sequel of the shonen anime Dragon Ball Super, Frieza is a greedy, tyrannical, egotistical monster.
2) Dio Brando (Jojo's Bizarre Adventure)
A shonen anime monster list without Dio would be incomplete. To sum up Dio's history across three parts of the shonen anime, Jojo's Bizarre Adventure, he was born to a very abusive father, Dario Brando. After being adopted into the Joestar family, he tried to expunge Jonathan by framing him for crimes, poisoning his adoptive father, and other horrific things even as a child.
Things only worsened when he became a vampire, started his coven with Jack the Ripper, and began a conquest of England. One of his most horrifying deeds is making a pregnant woman consume her baby when he turns her into a vampire.
He also survived for over 100 years, even after decapitation and being buried in a coffin beneath the ocean.
Dio's monstrous acts extend beyond his life and death, as he's responsible for the corruption of Father Pucci in Stone Ocean and the horrible fate of Okayasu's father in Diamond is Unbreakable. Perhaps it's for the best that the protagonist of the shonen anime Golden Wind, Giorno Giovana, never learned the whole truth about his biological father.
3) Sōsuke Aizen (Bleach)
Manipulative and backstabbing, the infamously overprepared villain of the shonen anime Bleach makes it here for the deceptive way he's introduced. At first, Aizen seemed polite, soft-spoken, and a loyal member of Soul Society. Then he stabbed his lieutenant Hinamori.
This lying, deceiving, cold-hearted man had been planning this for a long time. In fact, he had the Soul Society government as his puppets. He feels nothing for his actions, only satisfaction that he will become all-powerful with the Soul King's Power.
It was the only thing that mattered to him, even if that involved killing everyone in the way of that. This included his co-conspirator Gin Ichimaru.
All in all, Aizen is a monster - his ambitions may have been grand, but his arrogance was his downfall against Ichigo.
4) Shishio Makoto (Rurouni Kenshin)
Speaking of arrogance, pride, and monstrous acts, the more human shonen anime villain, Shishio Makoto of Rurouni Kenshin, combines Frieza's sadism and Aizen's arrogance into one person. Though betrayed by the Meiji government, Shishio made his ambitions clear: he would be emperor and have Japan for himself, and nobody would stop him.
Despite having friends and even a lover, Shishio saw everyone in his life as a means to an end. This is even reflected through his mummified appearance, which hides his burned body from when he was set ablaze in an assassination attempt by the Meiji government. He resolved to cleanse Japan in a fire with a warship that was thankfully destroyed.
Shishio's acts of wanton cruelty like enslaving a town, brutally killing his assassination targets, and slaughtering his way through Japan with reckless abandon earned him the right to be the successor to the Hitokiri Battōsai.
He met his end at Kenshin's hands, burning in a fiery blaze since he overtaxed himself. He was last seen in Hell with his friend and lover, vowing to conquer it.
5) Tamaki Tsunenaga (Deadman Wonderland)
An even more human, and thus even more inhumane, monster of a shonen anime character was the promoter and de facto tyrant of the shonen anime Deadman Wonderland, Tamaki Tsunenaga. To say Tamaki is a monster would honestly be sugarcoating it.
During the major earthquake that devastated Japan, his only concern was his games and computer and not his mother, who was heavily injured and needed aid. This wretch of a shonen anime villain only got worse from there, wanting to control and have as much "fun" as possible with the concept of the Deadman Wonderland.
Tsunenaga forced a man to throw a fight by killing his pregnant wife and grabbing the baby from her corpse. He was also the one behind framing the main character Ganta Igarashi and having him sent to that hellhole, and he then bowled with the former director's head.
The ultimate irony to this awful man was that he was never in control. The director Hagire Rinichirō used him as a pawn. Unable to handle being played like a chess piece, Tamaki chose to kill himself.
Poll : Are there worse actions committed by shonen characters then those listed here?