Having completed Chaos legion I dont remember Victor being incredibly powerful. Then agian it was a long time ago. But the guy used several blade attacks although the biggest annoyence was that you had to fight several other bosses after him without respite.
I talked to my bro since he beat the game.
He says that Delacroix gets his vote because he seems to have the edge over Seph:
he can summon minions, has the Apocrypha of Yzarc, shoots beams (omgzorz!), and his whole plan is more destructive than Sephiroth's Meteor idea.
The protagonist, Sieg Wahrheit, is a Knight of the Dark Glyphs who is on a quest to find his former friend Victor Delacroix, who has stolen the forbidden book Apocrypha Of Yzarc, and to stop him from releasing the spirit Azrail who will destroy the three planes of existence (the Nether World, the Middle World, and the Celestial World).