Karai

Before the "Enemy of My Enemy" episode, Karai was more calm and even offered the turtles a temporary alliance. But when they broke the pact, Karai became more cruel, more ruthless, and wanted to kill Splinter and the turtles at any cost, just like Shredder. Karai was also quite inhumane; for example, she wanted to kill the innocent April in revenge for her mother's death. She also treated those below her in rank, such as Xever and Bradford, with no respect.

Everything changed when she found out that Splinter was her real father, Karai became kinder, but she still remained vengeful and wanted to take revenge on Shredder herself, which ultimately led to her mutation.

In Season 4, Karai remained vengeful and did everything in her power to destroy Shredder. She was also quite overconfident and rarely enlisted the help of her friends, hoping to destroy Shredder's empire alone, which often led to her defeat.

Originally the daughter of Tang Shen and Hamato Yoshi, Shredder stole Karai when he killed her mother and set her house on fire. Splinter believed she was dead for the past 15 years. Karai believed Shredder was her real father, and Splinter was an enemy, like the Ninja Turtles, training under Shredder as a kunoichi.

Miwa has been well-trained in high-level ninjutsu and hand-to-hand combat since she was a girl. Her weapons are a tanto and several shuriken. Her natural combat skills make her incredibly agile in combat, even equaling Leonardo's high level of skill. At will, she can transform into a mutant snake.
Her snake form grants her several abilities, such as enhancing her hearing, speed, agility, stamina, stealth, and flexibility to superhuman levels, even granting her enhanced eyesight and night vision. Furthermore, Miwa can infect her victims with a highly toxic venom that is quite lethal within hours, but can be absorbed through the skin in seconds. When combined with her extensive ninjutsu skills and snake abilities, she becomes quite a formidable opponent. Some time later, Miwa learned to use her snake abilities to heal severe injuries she sustained (such as burns or bruises) by simply shedding the damaged skin and replacing it with a completely new one, similar to how a snake sheds its own.

New Girl in Town, The Alien Agenda, Revenge, and Foot Clan vs. Footbots are the only episodes where Karai appears wearing a mask.
Karai looks more like her mother Teng Shen.
Karai is the most unusual mutant of them all. After her mutation, she could change her appearance, even keeping her clothes. Immediately after her mutation, she could become human, but she couldn't change her eyes, teeth, or brain (meaning she thought like a snake). She only became fully human after some unseen procedure performed by Baxter Stockman.

Miwa has black hair that's lighter at the back. She wears several black earrings and red eyeliner on her upper eyelids. She has amber eyes. She wears a jumpsuit with silver armor, a black material worn under her armor, traditional Japanese shoes, and a purple belt.