Serial Killer Reborn

Natsu Shishke, a renowned maniacal sociopathic and sadistic serial killer, is beheaded fir his awful crimes. Waking up in a fantasy world, he discovers he had been reborn as the last, and most powerful, Shinigami. He adopts the name Kureijī Fumeteki, and embarks on a quest to become the one most powerful being- one kill at a time. Neither the Demon Lords, nor the God's, and their Servants, can stop him from becoming The Ultimate Being.