Doomsday and the Agent of Revenge

"We abducted you because we need you to save the world."

"...Say what?"

Upon opening his eyes, vigilante-for-hire Malice found himself in the bedroom of an unknown apartment. The last thing he remembers is being pursued by security police while fleeing a murder scene, then passing out from a tranquilizer. But he never would have expected to get such a bizarre request from this scarlet-eyed redhead girl calling herself "Phi"... Malice, a man who uses brutal methods to settle grudge after grudge for his various clients, hesitating not even to kill, was the one chosen by Phi, a phoenix descended to Earth from the heavens. Chosen for being the boorish murderer most suited to effectively teach her the hideousness of mankind. In other words, showing pure-hearted Phi how ugly people can be until she comes to hate them is the path to saving the world... Or so he's told.

(Source: MangaPlaza, edited)