In the Dragon Ball universe, Vegeta was previously a villain who gradually changes into Goku's trusted ally. Through their shared struggles, Vegeta and Earth's inhabitants become closer.
Rue Kuroha, or Princess Kraehe, initially tries to make Prince Mytho love her under the Raven's influence, but joins the effort to save him after discovering the Raven isn't her real father and is using her.
In Naruto, Gaara, initially driven by trauma to destroy others, changes after a heartfelt conversation with Naruto, choosing to protect people instead of harming them.
Through his relationship with Rin, whom he brings back to life, Sesshomaru changes from a vicious demon to a kind ally. As a result of his development, he helps Inuyasha and his allies battle Naraku.
Initially a rival and antagonist in Fairy Tail, Gajeel Redfox evolves into a loyal ally of the Fairy Tail guild after his defeat and subsequent friendship with Natsu Dragneel.