[Den-O]

Diends' powers are being blown waaaaay out of proportion, he cannot summon an army but he does have access to one in trios. That being said I'd probably have to vote for him based on the powers that he ACTUALLY has and has displayed. He would be able to steal the Hyper Zecter. I think we can all recognize that he'd probably take it before Caucasus would notice. All he needs to do is take it to another world and leave it there. Caucasus' biggest advantage is now shut down and he is primed for Agito to beat him.

Diend goes invisible and chills to the end. I think at this point the other 2 would be on even footing in the battle. But I believe Agito would come out on top, though injured. Then we get some Riotrooper cannonfodder while Agito is weakened. He takes them out with some degree of trouble after being nearly drained against Caucasus. Diend goes Complete Form for the finish.

I love Agito to death but I see this as the only logical conclusion to this battle.