Seymour is not as bad ass as Kuja or even Sephiroth, but he's still bad ass. He's strong unless you know you're gonna fight him. His hair isn't cool but the way he talks is.

Tidus-I never liked you from the first time we met.
Seymour-Oh my sincerest apologies.
Tidus-SEYMOUR!!

He's such a cool villain. The last battle with him, Seymour Omnis, the muic is the best in the game. Shame I had too kill him so fast.