I think we should put Arceus as a whole into S-rank. I mean it is one Pokemon after all, why should it have different tiers for different held items. It's like saying PsychoKiller Mewtwo is A-rank while Stalltwo is C-rank or something. When I play in Pokemon Showdown I don't know what Arceus form the opponent is running until they reveal it. Arceus's ability is what makes it so unpredictable and versatile. Also, Lugia in C-rank seems very wrong to me. It should be at least mid B consider that Lugia is the best general wall in the game.