[kupoartist]

To get the second overdrive, Energy Blast, return to Besaid once you've gotten
the airship. If you're playing the Japanese or American version of the game,
you will have no trouble. However, if you're playing the International or
European version of the game, you'll have to fight Dark Valefor. For a guide
on Dark Valefor, check out a PAL FAQ.

from an FAQ i have saved on my Hard Drive. Dark Valefor is a complete bitch, especially when you personally find the sidequests and leveling in FFX extremely tiresome (ie. no, i'm not going to jump no 200 lightbolts for the likes of you!)