Anima is by far the best Aeon in the game. Luckily the only one I missed was the one in Besaid so I beat Dark Valefor easy enough. If you want to have a chance with Dark Shiva You'll need the celestial weapons and Wakka's attack reels (try and get 12 hits every time). The Quick Hit skill may came in handy too. OH! Also: I think Dark Shiva can inflict death i think that can penetrate Deathproof. Ribbon is the only way to avoid that. Although I'm not sure about the ribbon thing, it was so long ago, it may be able to penetrate that too.