Kai (Ninjago Seasons 1-7, 9, 13-present)

Kai is one of the main protagonists of Ninjago. He is the current Elemental master and Ninja of Fire, Nya's elder brother, and Ray and Maya's son and eldest child. After the Time Twins kidnapped his parents at a young age, he and his younger sister worked as blacksmiths in the Four Weapons Blacksmith Shop for years until they met Master Wu shortly before Nya was kidnapped by the Skullkin Army. This leads Kai to learn Spinjitzu and train to become a Fire Ninja and successor of his father under Wu's guidance, in order to rescue his sister. After a successful training, he soon discovered his other teammates, Cole, Jay, and Zane, with whom he embarked on many adventures, battling the likes of the Skullkin and the Serpentine Army. After unlocking his true potential, Kai reflected his destiny of not becoming the Green Ninja himself after his days of training, but to protect and train Lloyd, who is destined to become one instead.

Why He Rocks

 * 1) He had great character development over the years:
 * 2) * He once started out as an arrogant know-it-all who believed he can do everything by himself, to a dependent member of the Ninja. Cooperative, responsible, and knows when to trust other people.
 * 3) * Had picked on Lloyd just for wanting to be like his father Lord Garmadon, has now destined to train and protect Lloyd as if he were his little brother.
 * 4) He is tough, confident, his good heart and dedication to people he cares about—if someone can earn his friendship, he will stop at nothing to protect them.
 * 5) As an older brother, he is very protective of Nya, the only family member to live with him after their parents were kidnapped by the Time Twins for years. Even after his sister's transition from Samurai X to Water Ninja and elemental successor of Maya, Kai is also supportive of her to become the "greatest weapon" against Morro and his Ghost Army.
 * 6) The way he used his elemental powers to fly were mostly inspired by a character from Marvel Comics, Iron Man.
 * 7) He had shared developed relationships with his teammates:
 * 8) * When he was first recruited by Wu to become a ninja. At first, Kai didn't care about training with Wu even considering him a crazy old man. But as the series went on, they grew closer. Kai and the other ninja cared about their master and is glad to have him mentoring them.
 * 9) * He and Cole respect each other and share several things in common such as their leaderships, confidence, etc. In "Peak-a-Boo", for example, he encouraged Cole to never give up when he is the one of the original four ninja who didn't learn Airjitzu.
 * 10) * He wasn't fully approved of Jay and his sister Nya's relationship at first, but as the series went on, Kai and Jay have shown themselves to good friends and work well as teammates.
 * 11) * He initially thought Zane was "weird", but when he found out that Zane was a Nindroid, he and the others supported and accepted Zane as their brother. They grow closer throughout the series.
 * 12) * Him and Lloyd weren't on the best of terms when they first met, but shortly after, Kai realized his destiny was to protect him. Though Kai was jealous that Lloyd was the Green Ninja instead of him, that doesn't hinder their friendship, and he doesn't end up to be like Morro (who also wanted to become one).
 * 13) Great performance by Vincent Tong, who also voiced Touta Matsuda from Death Note.
 * 14) Despite having no powers at the time, Kai showed intense loyalty through his determination to protect Lloyd when the latter was possessed by Morro.
 * 15) He had much better relationship with his parents. Even allowing his mom to spoil him rotten to the core.

Bad Qualities

 * 1) He was flanderized in seasons 8-12, where he tries really hard to be cool, spout out corny one-liners, and responding with "A pillow!".
 * 2) * Although, his character did recover in season 9, when Kai was serious enough to find a way back to Ninjago when being trapped by the Land of Dragons and was concerned at Jay's mental health.
 * 3) He can rather be cocky, or thinks impulsively at some times, but he does acknowledge his mistakes through and through.
 * 4) Like the rest of the Ninja as of Season 8, he lost his abilities of using Airjitzu and summoning his Elemental Dragon, so he won't look overpowered.

Trivia
He is voiced by Vincent Tong, who is mostly known for voicing Touta Matsuda from Death Note. in the movie, he is voiced by Michael Peña, who is mostly known for playing Luis in the Marvel Cinematic Universe.
 * He did not like technology most likely due to his past upbringing but he has been seen playing video games and indulging in other technical items, meaning it has grown on him.
 * Kai is very similar to Tanjiro Kamado from Demon Slayer: Kimetsu No Yaiba.
 * They both have younger sisters respectively (Kai with Nya and Tanjiro with Nezuko).
 * Their fire-based abilities are inherited by their fathers respectively.
 * They are friends with the cowards who use lightning-based abilities and fall in love with their sisters (Jay and Zenitsu).
 * They are also friends with the strongest ones who are obsessed with food and training (Cole and Inosuke).
 * They have parents who were taken away by their arch enemies (The difference is that Ray and Maya were captured by the Time Twins, Krux and Acronix, and Kie Kamado was killed by Muzan Kibutsuji).