Warning: Some Manga spoilers (Tokyo Revengers)With hundreds and thousands of anime characters, there are among the plethora of stories created, fans will be aware of the unique and well-written ones that stand out. While some characters come from animes that are not particularly popular in comparison to others, they all contain traits and aspects that set them apart from the crowd. Narratives such as One Piece are heavily reliant on its characters, and the manner in which they develop and function along with the world-building.
Whether significant or small, development and progression within anime stories are one of the main reasons fans continue to tune in, as this is what enables all of these narratives to maintain a fresh feeling without drastically changing other elements.
5 Katsuki Bakugo (My Hero Academia)
Fans of Kohei Horikoshi's My Hero Academia will be familiar with the dynamic between the main character 'Deku' known as Izuku Midoriya and Katsuki Bakugo. From the start of the series, Bakugo would always showcase an antagonistic attitude and behavior toward Midoriya even labeling him 'Deku', despite Midoriya's constant willingness to help and support him, which confused some viewers. With season 6 of the anime finally revealing the war between the villains and heroes and its aftermath, Bakugo's progression is on display.
Within a flashback during the confrontation between Deku and Shigiraki, it is revealed that Bakugo never truly understood why Midoriya wanted to help so much, which led to ignoring his own feelings of weakness leading to his bullying. In order to make up for what he put Deku through during their childhood up until U.A., he intends to stand side by side with him and support him in both training and hero work. It is now clear and obvious that Bakugo does indeed care for Deku, and always secretly has, especially after putting his life on the line to attempt to save him.
4 Takemichi Hanagaki (Tokyo Revengers)
Tokyo Revengers is one of the more unique stories among most anime, as the main protagonist Takemichi is not the typical badass or powerful fighter, but is rather the heart of the entire narrative. Early on in the story, Takemichi was far more afraid and less likely to engage in any form of combat, considering his lack of ability or power. Instead of Takemichi at the forefront of battles, it is his friends such as Mikey, Draken, Chifuyu, and all the other delinquents in Toman who engage in it all.
While this is very much still the case for the majority of the story, Takemichi eventually builds himself up to a stage of actually engaging within fights against monstrous and deadly figures, and despite nearly being beaten to death most of the time, he refuses to back down nor give up. This is mostly evident in the Tenjiku arc in the manga, where he decides to lead Toman into battle despite being handicapped without their leader Mikey, and also being outnumbered. Even when held at gunpoint and being shot in his foot, he refused to back down or show any signs of weakness, which sparked his allies to keep fighting.
3 Shinichi Izumi (Parasyte the Maxim)
Stepping away from Shonen anime, Parasyte the Maxim is one of the more graphic, deep, and realistic stories among many animes. Despite how it only being the length of one season, it still impressed a plethora of fans with its characters and storytelling leaving them wanting more. Given the cruelty of the world and the parasites taking over human bodies and using them as hosts, it meant nothing less than eventual heartbreak for the main character.
While Shinichi stopped one of the parasites from taking over his brain and kept it within one hand instead, it wasn't too long until this suddenly changed. After dying at the hands of his dead mother taken over by one of the creatures, Migi (parasite in his right hand) had no choice but to merge with his heart in order to save his life, which ultimately meant an entirely new Shinichi. Beforehand, he appeared far more timid and more in touch with his emotions, whereas once reborn again, a part of his humanity had vanished. Standing far more formidable and powerful, the story takes fans on a rollercoaster to eventually see Shinichi regain his human nature.
2 Robin (One Piece)
Initially upon meeting the Straw Hats, Robin was conveyed as a villainous figure working hand in hand with Crocodile in the Alabasta arc. While that was the initial assumption, Robin still took to sneak her way onto the Going Merry and requested to join the crew on their journey out to sea. This was at a stage at which Robin did not reveal much regard or affection toward the crew, an example being her labeling Usopp 'long-nose'.
After fans witnessed her painful and tragic backstory, Robin pours out her heart at Luffy and the Straw Hats showcasing her true love and friendship with them and the need of being saved from CP9 at Enies Lobby.
1 Monkey D. Luffy (One Piece)
Through the pre-time skip phase of One Piece, Luffy was regarded one of the more reckless pirates of the 'Worst Generation' despite his ability at the time to take down formidable enemies. This suddenly changed once witnessing the death of Ace, at the hands of the current Fleet Admiral Akainu.
While it was heartbreaking for Luffy, it was a crucial step in his progression as a character, as he learned that it was not possible to take on all enemies carelessly, and he must train much harder to protect those he loves. Luffy is still the lovable airhead many fans love, but is far much stronger at this stage of the story and knows when to take situations seriously utilizing his devil fruit abilities wisely.