I don't know shit about Sigma. A pyscho robot. Can he fly? Any other special abilities?

Seymour casts Protect on himself. I guess Sigma uses physical attacks so... Seymour turns into Omnis(Seymour X with Mortibody and Mortiorchis) Sigma charges and is deflected by Protect. His strength sort of dents the protective shield but it holds strong.

A cyborg is the most advanced version of a mechanical thing. Much stronger than a robot even. He would be weak against Thundaga right? Seymour could blast him a couple times with that.

From what I've heard he isn't that intelligent or quick. He wouldn't think of dodging Thundaga. Seymour could just continue this until he got enough power for Total Anihillation.

This attack would destroy the area around Sigma. He wouldn't be very stable considering his size. Seymour could then start firing Multi-Thundera at Sigma.

I almost forgot about the Mortibody. It could fire Desperado at Sigma. Shattering Claw wouldn't hurt Sigma though.

If Sigma survived this endless onslaught Seymour could cast the final piece in Sigma's destruction. ULTIMA!!! Sigma would blow up or something after that.

Now Seymour's defense is covered by his Protect and his and the Mortibody's Cura. The shield deflecting the brunt of the blow from Sigma and a Cura every now and then would keep Seymour well alive.

Seymour floats down to the body back in his normal state. Another victory was his. Another would be at hand soon enough....

Dnate... DANTE! DANTE! YOU ARE GOING DOWN!!!! YOU! ARE! NEXT!