i must ask this, which dark kiva

While I want to vote for Dark Kiva, I think Den-O could handle him.

Dark Kiva had three identities, with 2/3 of them being heroes. Your argument has been invalidated.

I went with Dark Kiva because even with Den-O's versatility, Dark Kiva's raw power and experience would be able to overpower the little peach-turtle-bear-dragonbrat-sometimes swan train man.

Three? How come I can only remember two (King and Otoya)? Who is the third?

new king

It says in the opening post that it's King.

Dark Kiva.
Den-O's versatility and unpredictability is useful, but he's lost on more than one occasion because of it as well, being unable to keep a solid advantage against opponents due to mass form shifting and bickering among each other.
And this isn't a fight where the enemy would run away during their bickering either. Dark Kiva would seize the moment and attack.

Oh. Well I feel stupid now. Derp.

While he was a new King, he wasn't called that... It was Taiga.

Anywho, I went with Dark Kiva. He's strong enough that, although versatile, Den-O would probably be beaten while the Imagin were busy bickering.

Den-O wins this one.