Challenge description:
http://www.femlob.com/redir/ff10nsgnsno/
Seymour Omnis is deceptively simple; he only uses Firaga, and will not stray from that path until you attack him five times. When you do, he uses Dispel and follows up with Ultima, which is a guaranteed OHKO.
Since he has 80,000 HP, you need to figure out a way to get rid of that within six turns; Supreme Gems don't always deal 9999 damage, so Auron and Lulu join in with Masamune-special physical damage and Blizzard respectively. The only catch, if one can call it that, is that Auron needs to get two attacks in; how that is done is shown in the video.
This is where my take on the challenge ends; I have too much going on right now to bother with Braska's Final Aeon and the inevitable chunk of luck you need to beat him. I know he's technically possible; I'm just not going to take a shot at the title right now. I'll record him eventually, though; my saved games aren't going anywhere.