Anime heroes are a complicated bunch sometimes. Rather than settle into the skin of a more traditional hero (at least based on Western philosophies), most heroes in anime culture tend to work in areas of gray to the point that the heroes and villains are almost indistinguishable from each other. Even if it is for the greater good, some anime heroes have committed questionable deeds that border on evil.
Among those borderline evil deeds, some heroes have gone as far as to kill their own parents. In some cases, the heroes had a good reason to justify it. Others? Not so much.
10 Setsuna - He Was Brainwashed By Ali al-Saachez
The moment that Setsuna's backstory is revealed in Mobile Suit Gundam 00, it is clear that his origin story is tragic. Like many children, he was kidnapped by Ali al-Saachez and trained to be a soldier. Under Ali's influence, Setsuna was manipulated to kill his parents in order to prove his devotion to God.
As if that wasn't traumatizing enough, Ali then proceeded to chuck Setsuna to the side and cast him out of the group when he no longer found him useful anymore. Ouch.
9 Goku - Becoming A Feral Great Ape
While Grandpa Gohan is not his biological father, he is the closest that Goku ever had to a father figure with his birth parents being destroyed along with his home planet, while infant Kakarot himself was orphaned to a foreign planet.
The real shame here is that just as quickly as it took Goku to crash land to Earth, he was just as quick to accidentally kill his guardian. Saiyans uncontrollably become mindless great apes at the dawn of a full moon and during Goku's first transformation, he accidentally stepped on Gohan.
8 Suzaku Kururugi - Wanted To Prevent Senseless Killing
Contrary to his actions, Code Geass' resident anti-hero was never a fan of senseless killing and that was reason enough why he opted to kill his father. His dad was Japan's final prime minister before the Britannian Invasion. Suzaku soon learned that his father was willing to selfishly work with the enemy and, in turn, kill Japanese officials and citizens. In a fit of rage, he stabbed his dad in the chest.
Often a pivotal moment like this turns someone into an irredeemable villain, but in Suzaku's case, it only motivated him to try to become a better person by, thus, atoning for his sins.
7 Kiritsugu Emiya - For The Greater Good
Another anti-hero whose motivations and actions continually blur the lines between hero and villain, Kiritsugu Emiya has done things that would make -- some argue -- him to be a bad guy, but as the main protagonist of Fate/Zero, everything he's done was for the greater good, including killing his parents, respectively.
First, he killed his father to prevent the man from becoming a Dead Apostle. Meanwhile, he had no choice but to kill his mother in a last-ditch effort to stop a plane full of ghouls, which his mother happened to be boarding. And by shooting the plane out of the sky, he was forced to end his mother's life.
6 Kohaku - Possessed By A Demon
There was once a time where Kohaku would not so much as harm a fly. That is until he was possessed by a demon named Naraku who decided to use him as a meat puppet to accomplish his evil bidding. Included among that evil bidding was forcing Kohaku to murder his father who Kohaku loved dearly.
One thing that Kohaku did not love was being forced to pierce his old man through the neck with a chain sickle. The whole ordeal was traumatizing enough for Kohaku to decide to become a demon slayer.
5 Arren - Possessed By Uneinheit
Arren in the Tales from Earthsea was in a similarly unfortunate situation as Kohaku was in Inuyasha. Here, Arren finds himself possessed by an evil presence called Uneinheit that manifests itself as an evil mirror image and a carbon copy of himself.
While under the influence of Uneinheit, he unexpectedly stabs his father, the King. Engrossed in the shock and confusion of it all, Prince Arren steals his father's sword and flees the castle. He is continually haunted by this image until he returns to the castle to atone for his crime.
4 Lelouch vi Britannia - His Father's Misguided Views
Suzaku Kururugi is not the only protagonist in Code Geass who killed their father. Lelouch is another. After his father's hubris and twisted views on justice as an emperor led to Lelouch being banished from Japan at the age of 10 after asking his father why he left his mom defenseless for her inevitable assassination, he came into direct conflict with his dad.
When he became older, upon realizing that his dad's motivations and actions would ultimately lead to mankind's destruction, he turned the Gods against the emperor, leading to his dad's death.
3 Eri - Erased Her Father With Time Travel
In My Hero Academia, quirks work more or less like superpowers that have the potential to alter reality. In some cases, these abilities can be a blessing, but in others, they are a curse. For Eri, they fall into the latter case.
Eri has the ability to turn back time to the point that it drastically alters the present, something that she struggled to control when she was but a small child. As such, she ends up changing time enough to erase her father from existence, compelling her mother to abandon her.
2 Eren - His Dad Turned Him Into A Monster
Much like Goku before him, Eren did not kill his parent out of pure free will or desire, but because he transformed into an uncontrollable monster. It happened when the Attack on Titan star was injected with Titan serum by his own father.
Knowing that this was the only way that his son could become a Titan shifter, he allowed Eren to become a Titan and when he briefly became a Titan, he ate his dad, something that he failed to even remember or know until long after the fact.
1 Yuno Gasai - Her Parents Starved Her
In contrary to most of the parents mentioned on this list, Yuno Gasai's parents were actually terrible people. To say they deserved to die might be harsh, but it's hard to blame Yuno when readers understand her upbringing.
As detailed in Future Diary, the more that her parents became stressed about money, Yuno's parents would keep her in a cage and starved her practically to death in hopes that their discipline would mold her into a "perfect citizen." When she becomes tired of the abuse, Yuno locked her own parents in the cage, leaving before they starved to death.