Original God, Fatui Zero Executive Officer

Plot-oriented + with a knife + the protagonist is both good and evil + there is a female protagonist

PS!!! You need some IQ!

Timeline: Came to Teyvat with Yingkong, woke up with Kong in the Kanreya era, challenged Tianli alone, was defeated and died, was taken away by the Queen of Winter and his body was revived, but he lost most of his memories and became the 0th executive of the Fatui [The Dead].