While many viewers hate them, mentally unstable anime characters are great for injecting unpredictable plot twists and character developments (which all anime fans love).
These crazy characters may have lost their sanity to some degree, but the stories behind their loss can be eye-opening, heart-breaking, and soul-rending—so much so that you may even start to pity them.
Mentally unstable anime characters aren't limited to those who simply run wild and kill on a whim. There are also those who possess manic obsession over someone, or maybe they're driven mad by a singular goal, or they could be manipulated by a greater power.
From psychopaths to suicidal maniacs, here are some of the best mentally unstable anime characters we've seen.
13. Alisa Amiella (God Eater)
Alisa is one of the two new-type God Arc wielders in God Eater, and one of the best god-eaters in the group. Though she can wield and utilize her weapon effectively, she has a dark past that lingers over her.
Because of that trauma, she's mentally unstable and was even used as a killing machine after being manipulated by a scientist she works with. There even came a time when she was ordered to kill Amamiya during a mission, which she unknowingly obeyed.
12. Tomura Shigaraki (My Hero Academia)
Tomura Shigaraki wasn't always the villain he was; he only became this way after experiencing a disaster after he awakened his Quirk (Decay). All for One managed to turn Tomura Shigaraki's personality into the badass villain he is now by exploiting his trauma.
And because he's a bit off and tends to get irritated by unexpected situations, he frequently scratches his neck as he itches to annihilate people. It's a good thing he has Kurogiri by his side.
11. Gaia (Baki the Grappler)
Gaia from Baki the Grappler is one of the more fearsome fighters. He was the other personality of Nomura, who was seen to be the medic of the 1st Airborne Brigade of Hokkaido.
Because of his split personality, Gaia and Nomura have different fighting abilities and different drives to fight. Later on in the story, Gaia somehow managed to conquer (and merge with) the other personality, showing a more composed and formal person.
10. Shuu Tsukiyama (Tokyo Ghoul)
Shuu Tsukiyama (also known as the "Gourmet") only wants the finest as his meal, whether humans or ghouls. As long as his quarry catches his attention and interest, he'll go after it.
With this obsession over his best meals, he took an interest in Ken Kaneki, who was a hybrid of human and ghoul. We even saw him go insane as he sniffs a handkerchief stained with Kaneki's blood.
9. Gaara (Naruto)
We're talking about the young Gaara, who was filled with hatred and bloodlust (long before he met Naruto). Though he was born as a normal child, his father made him into the vessel for the One-Tail Shukaku, thus giving him a life full of murder at a very young age.
In his younger years, he trusted no one—not even his siblings—and would kill anyone without remorse.
8. Sister Krone (The Promised Neverland)
Remember the adult who was sent to the Gracefield House to keep an eye on the children? The one who talks to her doll? That creepy woman was Sister Krone.
Though she was seen as mentally unstable, her acts of bringing down Isabella for her sake somehow managed to help the children escape their fate of being food for demons.
7. Adult Gon (Hunter X Hunter)
Though he was as strong as the Chimera Ant King, this big guy lost his sanity for the sake of revenge. We saw this when he pounded the already pulverized head of the feline Royal Guard to nothing just to satisfy his internal anger, loneliness, and depression.
6. Shigeo Kageyama (Mob Psycho 100)
He's calm, composed, and formal—but it's to keep a wild power from erupting in his body. Once this boy can't handle his emotions and anger, be prepared to witness a badass rage moment.
5. Hisoka Morrow (Hunter X Hunter)
Why is Hisoka on this list? Because... he's crazy. It's as if we never know what he's up to, and he's frequently up to something that brings all kinds of unexpected twists to Hunter X Hunter.
He may appear calm, sometimes funny, but there were also times he appeared murderous and ready to kill. We saw him charge mindlessly during the Hunter Exam in the scene where Gon managed to steal his tag.
4. Osamu Dazai (Bungo Stray Dogs)
He was a former top executive of the underground organization Port Mafia, but now he's an agent in the Armed Detective Agency. He has this Gift that nullifies the abilities of those whom he touches.
He earns a spot on this list because he's a suicidal maniac (with a twist). No man with a normal mind would want to commit suicide all of a sudden, with some beautiful girl by their side (what Dazai calls "double suicide").
3. Yuno Gasai (The Future Diary)
Many envied Yuki Amano for having a perfect girl like Yuno Gasai. But that girl has some dark secrets up her sleeves.
She was a brutal murderer and can go on killing sprees, slashing indiscriminately without any guilt. This murderous intent resulted from the abuse and mistreatment she received prior to the series' main timeline.
Many reviews about The Future Diary and Yuno Gasai state that she shows symptoms of some interpersonal or antisocial disorder, where she's only open to Yuki and no one else.
2. Midari Ikishima (Kakegurui)
Another suicidal maniac/psychotic character, Midari Ikishima has a masochistic personality that brings her to play and gamble with life-threatening games like it's no big deal. She even stabbed her eye out with a pen just to pay her debts.
1. Shou Tucker (Fullmetal Alchemist: Brotherhood)
Consumed by greed and power, this Alchemist is universally hated by pretty much anyone who watches Fullmetal Alchemist: Brotherhood. Indeed, he's easily one of the most hated anime characters in history, so much so that we have to conclude that he's insane.
Shou Tucker, the Sewing Life Alchemist, used his wife to create a chimera capable of human speech. This guy lost his mind and even used his young daughter for his inhumane experiments.