I think that the easiest way to kill evrae is to use rikkus overdrive and choose 1 underdog's secret and 1 lvl3 or lvl4 key sphere. it makes trio of 9 and you only need to know the language of al bhead. if you can speak it just talk to rin in the airship.
But that would mean the only quick way to defeat Evrae involves playing it the second time or using someone else's memory card and one of those sphere things that puts the primers from a different save onto your save...