Keyaru

The primary protagonist in Redo of Healer is Keyaru, who goes by the name Keyaruga. He was selected as a Hero, the Hero of Healing, on his 14th birthday. Keyaru was at first a really good and sensitive boy with dreams. He was thrilled to learn that he was one of the heroes who would save the world, but when he realized that by curing people, he was also absorbing their memories and suffering, he became fearful of using his power. But when he witnessed their dark side while being tormented by them while under the influence of drugs, all he wanted was retribution.

Keyaru's kind personality fully turned into that of a man who was vengeful, harsh, ruthless, unstable, sociopathic, relentless, bloody, and sadistic after being betrayed, imprisoned, drugged, tortured, beaten, and raped by numerous individuals who wanted to break their level limits for a protracted length of time. Keyaru changed his old mentality into that of a clever and manipulative misanthrope because his innocent personality was what allowed him to be exploited.

He used his abilities to exact revenge on each victim one by one in ways that went beyond the point of no return. Keyaru's greatest hero, Flare, who later turned into his greatest foe, was the person he adored the most. To repair them and begin again, Keyaru took immense joy in breaking each of Flare's fingers.

Anime: Redo of a Healer