His current nickname sounds much creepier in light of today. He's a very stealthy guy and wears a skull styled helmet. He's the kind of guy that's not the bad guy but he's a monster at the same time. https://www.notebook.ai/plan/characters/576514/edit
If I were you I'd give him a distinct calling card or signature and then name him after that. right now he doesn't have much setting him apart from any other edgy serial killer who's real good at literally everything. Something like he always carves a certain symbol into his victim's skulls so he's named after that symbol, or he always leaves something like a feather or a pair of classes so he's called "The Raven" or "The Oculist" or something but that's just my two cents. feel free to completely ignore all that