Originally Posted by
SpoonyViking
Duel field would actually be more disadvantageous to Achilles than to Cú Chulainn, though. And his speed NP doesn't make him the Flash; he runs fast, but we have no indication he fights at the same speed as he runs, otherwise his fights with Siegfried and Chiron, for instance, would have been very different. (This has got to be one of the most misunderstood NPs in the franchise.)
As for the shield, that one I can't really comment on; that volume hasn't been translated yet, so I've only seen that part in the anime. I do think Gáe Bolg would be invoked faster, though.
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I'd say Achilles' best bet is to fight smart for a change, like he does against Chiron. If he fights more like the Rider he is, or if Gáe Bolg is somehow taken out of the picture, he should have much higher chances; the Cú Chulainn we've seen is too nerfed from being summoned outside of Europe and having Kirei as a Master.