Kozlov was far better as a heel than a face. He was dominant, impressive and powerful. It's just stupid that WWE refused to use his ***** background and to let him use some ***** moves. He was made to be the new "Russian bad guy". I could imagine him being undefeated during at least 6 months in one Goldberg's streak in WCW.
And it was utterly stupid to quickly make him Santino's partner as they did. The best thing to finish his heel reign would have been to make one "Rocky Balboa versus Ivan Drago" feud between them.
Santino was basically the Rocky Balboa of WWE, one unknown Milanese guy considered as an underdog who suddendly turned champion. He had the audience's sympathy and was a good wrestler. Kozlov was undefeated and powerful, one perfect Ivan Drago. This feud could have created some great matches and good dramatic tension.
Later or during the georgian crisis :
WWE could even have tried to turn them friends later in one "Rocky and Creed versus Clubber Lang" way :
Kozlov becomes Santino's trainer (and not his smiling comedic friend) in order to help him to defeat one bigger opponent. Kozlov stays one heel but decides to help cause he respects Santino as one good fighter.