It's possible for the entire human race to be eliminated with a single blow. The scenario is scary to imagine, yet it's a common plot point that pops up time and again in anime. In particular, shonen anime frequently showcase their most epic villains' sick strength by having them kill millions of people with the wave of a finger.
Although the medium is known for featuring bright colors and cute characters, anime genocide is shockingly ubiquitous. To make matters worst, many of these atrocities occur as the result of a single attack, wherein countless lives are lost in the blink of an eye. After watching the world unceremoniously fall apart in The End of Evangelion, you'll probably want to go home and hug your loved ones.
There are so many horrific killings in Blood-C that choosing just one is nearly impossible. Nonetheless, there is one infamous scene that involes demonic Bunny beasts killing innocent townspeople in unbelievably gruesome ways. They break their victims' legs like chicken wings, and skewer their soon-to-be lifeless bodies like kebabs.
This is all pretty vomit-inducing, yet the Bunnies' most shocking act of violence comes when they gather all the townspeople up in a sack and puree them like a blender. There's a reason why these evil Bunnies are among the scariest anime monsters of all time.
Civilians and soldiers alike are massacred in the beginning of Attack on Titan; the slaughter begins with the fall of Wall Maria. Thousands of city residents are wiped out in the attack, and 250,000 soldiers are sent off to die in a failed counterattack.
The horrific event perfectly establishes the stakes for the adventure, as it demonstrates the raw, destructive power of the Titans.
While the original Fullmetal Alchemist series features Dante as the final villain, the 2009 series FMA: Brotherhood sticks more closely to the manga and introduces Father, one of the smartest anime villains of all time. Father is birthed from the blood of the powerful alchemist Van Hohenheim, who is later manipulated by Father to bring about the destruction of the Xerxes Civilization.
Father uses the lost souls of the Xerxes Civilization to transform himself into a living philosopher's stone that resembles his human puppet Hohenheim.
Out of all the Dragon Ball Z villains, Freiza is perhaps Goku's most memorable nemesis. His mere presence makes even the strongest DBZ fighters quake in their boots, and for good reason. At the time of his introduction, Freiza is the most powerful being in the galaxy, and is responsible for the destruction of Planet Vegeta.
Freiza destroyed the Saiyans' home planet out of fear that the legendary warriors would rise up and defeat him. Of course, DBZ fans know that despite Freiza's best efforts, that prophecy comes true in the form of Super Saiyan Goku.