There should be a difference between being "possessed" By a dark spirit, and having a dark side. Kyouya was and is the character that TT meant to be the "Kai" of the newer generation. Kyouya's intro to the series was quite similar to that of Kai's was it not?
Besides that, Kyouya was always the one out for blood when it came down to getting to the top in a tournament to defeat Hagane Ginga. Kyouya's character traits are similar to those of Kai's and for something's sake, he had his own "gang" like Kai did.
Tsubasa should be eliminated from this vote seeing as though his characteristics follow Ray closer than Kai. The whole "where'd my eagle fly off to?" thing when he got possessed should further this.