Dio is a very foul mouthed and aggressive character who seems to find joy in other peoples suffering and just being a very pettunlant little shit as a youth, as he gets older he starts to mellow out a bit but still retains a large amount of these qualities but also becomes more cunning and attempts to hide this more easily but once he turns into a vampire, he goes full all in on this wrathful desires and attempts to savagely and horrifically kill everybody in his path in the most sadisitc path ever.

He should have a charasmatic voice but have it dripping with some level of venom at all points, feel free to experiment with it.