The power of friendship is one of the most important storytelling elements in an anime. In some anime, it's so important that they had to introduce the false friend trope in order to make the true friendships stand out better. And besides, the best villains are the ones that used to be friends, or at least whom the protagonist believed to be their friend.
The thing about false friends in anime is that they reveal themselves in a grand and messy manner. When a "friend" decides to shed off their mask, it's usually a bitter cocktail of tears, anger, and trauma—the perfect recipe for an anime protagonist's breakdown. As such, there's no shortage of that along with false friends in the following anime.
8 Otome's Needs New Friends (School Days)
Heartbreaking doesn't even begin to describe what happened to Otome Katou during her high school years in School Days. Her three friends, Kumi, Minami, and Natsumi (also known as the Trio) befriended her just to enact some horrible crimes on her. The most serious offense was secretly recording a video of her during intercourse with Makoto, a guy she likes.
As if that wasn't enough, all three of Otome's aforementioned fake friends all slept with her Makoto, practically feeding Makoto's serial cheater tendencies. Sadly, the betrayal for Otome didn't stop there as the Trio also leaked the recording to the whole school.
7 Kaworu Made Shinji's Life Even Worse (Neon Genesis Evangelion)
Shinji in Neon Genesis Evangelion just could catch a break. When he finally found a friend he could confide in and share his emotions with, Kaworu turned out to be the 17th Angel, which is an enemy Shinji is supposed to kill. Granted, this whole friendliness shtick was Kaworu's mode of operation as an Angel.
Shinji only later found out about Kaworu's true nature and intentions. The more miserable part for Shinji was that he was the one who had to kill Kaworu by squeezing the latter into a red past with his giant mech. That was likely the last straw that made Shinji lose his mind and what was left of his resilience.
6 Kaede Kayano Was An Alien Assassin All Along (Assassination Classroom)
Assassination Classroom is no stranger to surprises and sudden plot twists that seemingly came out of nowhere. One of those was Kaede Kayano, an initially innocent student in Korosensei's class. But it turns out she wasn't a student at all. She was an actress who dressed up as a student for a chance to assassinate Korosensei.
More than that, she also underwent a similar procedure that turned Korosensei into a living weapon. Her reveal was one fraught with a sad backstory involving her sister's death for which she blames Korosensei, fueling her drive for revenge. Thankfully, Korosensei has a knack for fixing relationships and problems, but everyone who knew Kaede as a student likely has trust issues after knowing her true self.
5 Light Yagami Has No Shortage Of One-Sided Friendships (Death Note)
It's rare for an anime to explore the false friend trope through the lens of the actual false friend but Death Note is a rare anime anyway. Light Yagami is the false friend in question here and throughout the series, he's made and maintained "friendships" for the sake of using friends as tools and strategic advantages.
The most worrying victim was Misa Amano who was also madly infatuated with Light. Just seeing Light use her lifespan as a resource was upsetting enough. What's even more painful is how one of Light's most dangerous enemies, L, considered him a friend and even took a liking to him. But in the end, Light didn't believe in friends; only in tools, considering he's also one.
4 Lelouch Countered Rolo's False Friendship (Code Geass)
Lelouch is quite used to betrayals both tactical and casual, but the one he suffered from Rolo's hands is more traumatic than the rest. Because Rolo was a spy and assassin whose job was to keep Lelouch in check. Lelouch found this out prematurely and turned the tables on Rolo's false friendship by being a false friend himself.
However, this took a toll on Lelouch and by the end of his ordeal, he had a mental breakdown and threw all the psychological hurt he could at Rolo, claiming that he's always hated him. Hence, this twin case of false friendship went down in anime history as one of the most convoluted pretend plays.
3 Aizen Has Always Been A Main Antagonist (Bleach)
Aizen is often hailed as one of the most manipulative and sinister villains of all time. As one of the main antagonists in Bleach and its numerous arcs, Aizen ticked off a lot of villain tropes, including being a false friend to everyone in the Soul Society. He was one of the most esteemed leaders and figureheads in the Soul Society, after all.
Then, like a bolt in the dark, Aizen suddenly revealed to everyone who knew him as a friend and ally that he had been hatching a plan all along, and that every connection he had in the Soul Society was never sincere. This etched him in the annals of anime villains as one of the most successful, at least in terms of execution.
2 Reiner & Bertholdt Had A Gigantic Secret (Attack On Titan)
Reiner & Berthholdt's revelation came in earlier than expected in the giant-filled anime, and even then, it was surreal and humorous. Reiner casually admitted to being a spy out of his brewing split personality disorder. So there was a certain shock value to their reveal and the heartbreak likely didn't set in immediately.
But over the course of the anime, the toll of Reiner's betrayal and false friendship was emphasized further through his guilt and depression. It taxed him just as much as it did his allies back on the island of Paradis, perhaps even more so. And Bertholdt? Well, he's resting in Armin's belly, since that's probably the only thing that can stomach his name.
1 Griffith Valued His Ambition Over His Comrades (Berserk)
All these betrayals pale in comparison to the ultimate false friend reveal courtesy of Griffith from Berserk. Because from the start, Griffit, a poor peasant kid from the slums, had dreamt of having his own fantasy kingdom no matter the cost. So he formed his own mercenary band and precisely carved his way to the top of the feudal hierarchy with the help of his comrades. They viewed him as some kind of messianic figure.
But at the end of his journey, Griffith ended up sacrificing all his comrades in the Band of the Hawk for a shot at godhood. There was no hesitation on his part, meaning he never valued the mercenary family he created. The chaos he caused and the mountain of corpses he sacrificed to achieve his selfish goal make him one of the worst false friends and betrayers in the history of fiction.