First u have 2 place all of ur aeons into overdrive mode. den place ur strongest pplz with
high damaging overdrives to their overdrive mode. also have dispel and holy waters so dat
u dont die 2 easy. during the battle use all of your overdrives and have yuna cast protect
and all dos protective spells. den try to use all of your overdrives . dont use em 2 long
though. then once the time is rite hit him with all your aeons overdrives. makes 9999 dmg
+ the absorbing thing making it bout 13999 dmg but it gets lesser and lesser.

if u take too much dmg use al bhed poitiots

when i face seymour the 2nd time i was freaked out by how easy it was he was like the
easiest boss EVER!!!!!!!!

im the same im having a hard time defeating seymor the second time right now im trying to
find the ability to reflect on the spere grid i cant seem to find it

Get near a one of the save sphere and fight a battle then save do a nother battele then
save you get the idea keep doing this till everybody has overdrive mode including aeons go
to the boss and make tidus use hastga one time or hast one time one the people your
fighting him with make shure you have yuna on the battle feld make yuna summon the aeons
and make them use there overdrivs if that doseint kill him then use your partys overdrives
thats how I beat any boss.