By far Dorohedoro's greatest strength is its incredible and unique world, which feels grimy and lived-in and unlike anything you've seen before. The closest comparison I can think of is... Planescape: Torment ↗, maybe? It's an absolute delight, and most of the 'rules' don't make sense and it doesn't matter. You want to spend time with the world and you want to spend time with the characters in the world, who are all pretty fascinating & well-developed.
The overarching plot is interesting though at times intentionally circuitious. The anime has a lot of fun playing around with conventions (the mafia episode! the carnival episode! etc.) and the violence feels stylistic; it's a fairly warm show when you strip away all the blood.