Lionheart
Solid Ocelot
Devil Arms not part of their owner, Nero's Devil Bringer is. So it would be reasonable to say that objects absorbed by it are part of Nero and that he is more demonic than he was at the start of the game (to a very limited degree and without making him less human)
I'm going to have to go by what the game says. The things he absorbs with his Devil Bringer can be compared to the things Dante absorbs (and he does seem to absorb them), namely the demons themselves (Echidna, turns into gauntlets, Berial, turns into Lucifer, etc). It's just that Nero gains abilities, whereas Dante gains weapons. Not once was it implied that Nero got more demonic by absorbing the Rusalka Corpse, Sephirothic Fruit and so on. Nor would I expect him to become more demonic by absorbing a corpse No, the question was really whether he got biologically demonic by the end of the game. I suppose he didn't change, he just gained new skills and eventually accepted he was (partly) a demon.