Anime is perhaps best known for its over-the-top antics, with ever-increasing power levels and unpredictable plot points each ranking highly among the medium's most overused tropes. When it comes to the latter, there's arguably no method more effective for shocking and surprising viewers than a good old-fashioned anime betrayal.
What makes the act of backstabbing so deplorable is that it's easy for viewers to empathize with those who are on the receiving end. In fact, a lot of the time, it can feel as though fans are being betrayed just as much as the victims themselves, especially if the person behind the betrayal has been part of the show for a long time.
Frieza Destroys Planet Vegeta (Dragon Ball)
Despite being one of the longest-running anime series of all time, Dragon Ball rarely explores the theme of betrayal. That's not to say that it never comes up though, with Vegeta stabbing many backs during the first few sagas of Dragon Ball Z. In his pursuit of the Dragon Balls and ultimate power, the Saiyan Prince is responsible for the deaths of Nappa, Cui, Zarbon, Dodoria, Guldo, Burter, Recoome, and Jeice; all of whom had previously fought alongside him. However, his betrayals are nothing when compared to Frieza's.
Concerned by the rumors of a Legendary Super Saiyan rising up and freeing the Saiyan people from his tyrannous rule, the Universal Emperor decides to take matters into his own hands. Well, technically, his own finger. With one powerful energy ball, Frieza destroys Planet Vegeta, and, along with it, thousands of Saiyans who had previously helped him to seize control of the entire universe. Among them were many innocent women and children, making his betrayal all the more shocking.
Aizen Betrays the Soul Society (Bleach)
That somebody would betray their allies in order to seize power for themselves isn't necessarily that surprising in and of itself. After all, nothing corrupts quite as effectively as power and the pursuit of it. However, in the case of Aizen, who had previously come across as such a loyal and diligent captain, his decision to abandon his post comes as a genuine surprise, as too do a lot of his subsequent actions in his quest to overthrow the Soul King.
It could perhaps be argued that his actions don't technically count as a betrayal as he was never officially allied with the Soul Society. That's certainly the way that he sees it, anyway. However, it's clear that those impacted by his sudden heel turn see things very differently, just as anybody in their situations probably would. Like most fans, nobody saw it coming, making it one of the best anime plot twists of all time.
Reiner & Bertholdt Reveal that They're Titans (Attack on Titan)
Perhaps had Annie's big Female Titan reveal come a season or two later it would be seen as the bigger betrayal. In the end, however, it ended up being just the first of many big backstabbing moments to rock the world of Attack on Titan. The biggest of these betrayals arguably came midway through the following season, when Eren learns that Reiner and Bertholdt were the Armored and Colossal Titans respectively.
Fans of the series were just as taken aback as Eren was, particularly when the pair try to get him to join them. It then transpires that the duplicitous duo were likey the ones who helped Annie to track Eren down and an epic multi-episode battle quickly ensues. The fact that both Reiner and Bertholdt had been a part of Attack on Titan since the very beginning and had played such a pivotal role in the story made the reveal particularly shocking, and, as a result, one of the best anime betrayals in recent memory.
Sasuke Sides with Orochimaru (Naruto)
When it comes to great anime betrayals, few series can compete with Naruto. There are plenty of memorable moments to choose from, like when Itachi decides to slaughter his own parents and the rest of the Uchiha clan, leaving only his little brother Sasuke behind. This clearly leaves a lasting impression on the young Sasuke, who would later go on to commit several major acts of betrayal of his own.
As well as turning his back on Naruto at the end of Naruto: Shippuden, Sasuke also stabs his fellow Child of the Prophecy in the back during the first part of the original Naruto anime. The latter is arguably the more shocking of the two, as, up to that point, Naruto and his friends had been risking their lives to rescue Sasuke from Orochimaru's clutches. Instead, he decides that he'd rather be the Legendary Sannin's apprentice and then goes on to face off against his former friends before finally coming to his senses.
Griffith Sacrifices His Friends (Berserk)
The very best anime betrayals are the ones that nobody sees coming, which is certainly the case with Griffith's in the Berserk anime. The Band of the Hawk's leader is locked away following his affair with Princess Charlotte, but his loyal friends and followers refuse to give up on rescuing him. However, as they soon learn, something inside Griffith changes during his time imprisoned in the Tower of Rebirth.
Griffith's obsession with power leads to him sacrificing members of the Band of the Hawk to appease the God Hand. What follows is one of the most one-sided anime fights of all time, with the monsters that he summons able to tear through his former comrades like tissue paper. By the time he emerges as Femto, all but Guts and Casca have fallen. Not yet satisfied with the sheer scale of his betrayal, however, he then proceeds to violate Casca while Guts helplessly watches on.