Maybe I missed it somewhere but on all of the villain sheets the last stat at the bottom is the Evil Score. For shredder it is 99, for Ult. Shredder it is infinite.
Where is this value used in the game?
I don't think it is used. It's just for fluff like the lore quotes commonly found on card games. It does give some indication of the likelihood of seeing a good guy version of some characters in the future, though (hint, hint).