Hear me out on this one:

- Main Character is a nerdy looking boy who studies theology at a university
- Target: Atheists, cultists and non believers in general
- Instead of a Shinigami, his guardian angel will assist him
- The antagonist is a witch who forms a team with other witches in order to find the murderer
- No Death Note. The MC uses his guardian angel to manipulate his victims into suicide or even murder specific victims for him

Let me know your thoughts as well as your suggestions in the replies