He wants Cena to be a menace, aka heel.
Last night on Raw, Cena was the subject of "We All Hate You" chants. As he was confronted in the ring by the recently dumped Zack Ryder, Cena removed his "Rise Above Hate" shirt signifying he was starting to lose ground in his campaign against hate. He even alluded to smacking around the injured and brokenhearted Ryder making us believe Kane and the fans are getting to him.
The goal is to make Cena wrestle out of "Malice. Selfishness. Rejection." as opposed to "Hustle. Loyalty. Respect."
Originally Posted by Callumomac
I like your explanation, but I still have reservations about making predictions for this match. I do think that Cena becoming a monster makes an interesting plot device to the Rock/Cena feud, though.
It's a pretty good storyline, actually.