Obtain Vilucha without having to fight the dark aeon?

I have the HD Remaster version. I am trying to go back to Besaid to get Vilucha to use with the Blitzball games. I realize they added Dark Aeons, but at this stage in the game they are too hard to defeat. Is there anyway I can get Vilucha without having to fight Dark Valefor?

I'm afraid not. Entering Besaid triggers the cutscene, and forces you to fight Dark Valefor. There's no way around that. So come looking for a fight, and bring your best weaponry.

If Wakka's been levelled enough, a perfect Attack Reels with a Break Damage Limit weapon can drop it without any issue. Otherwise, you're in it for the long haul. It has 800,000 HP, and will require a team of heavily levelled members in order for them to survive. Break HP Limit and Auto Phoenix on one person can help you take him, and give you the edge when someone drops.

If you're still having difficulty with the dark aeon I recommend using Yojimbo's special Zanmato. Save at the closest save point and grand summon him with Yuna (if speeds an issue equip someone with first strike and swap them for Yuna once the battle begins.) If you give a million gil you're likely to get it, but the odds of him using it depends on how often and well you use him after you've gotten him. Good luck