I have to disagree. Riku doesn't have his dark form in Kingdom Hearts 2 and Kadaj's swordplay is fast and elegent. Kadaj has energy beams that seem to be pretty powerful if it can force Cloud to his knees when the attack missed (not by much). Plus if anything this fight will come down to a sword fight and I don't think Riku could equal or prove better in swordsplay then Kadaj.
The energy from the explosion caused by DiZ's machine restores Riku to his "true form", revealing an older Riku still cloaked and blindfolded, which he removes to reveal a new outfit. After this, Riku becomes a selectable party member for the World That Never Was. His Soul Eater changes into a Keyblade, which he names "The Way to the Dawn". Sora and Riku’s co-op move, Eternal Session, is the most powerful team attack in Kingdom Hearts II. The final boss battles against Xemnas are fought by Riku and Sora alone.