Ps3 here. I have played the map many times now killing every enemy. Even the snowmen and many cannons at the end have fallen and I have yet to get it. This star plus the ones from the unreleased dragons peak are all I have left.
Play as Sonic Boom and take her skill path with the birds.
Throw eggs against a wall and have the birds fight off every enemy in the stage. By the end of the stage they will have died so many times they count towards the enemy goal.
I did this for Quicksilver Vault and had the Enemy Goal at the 40% mark in the stage, I just ran past all of the enemies and FINALLY got 100% game completion.
I haven't played Empire of Ice yet but I'm assuming the same strategy will fix the glitch of their not being enough enemies in the level. When her birds die, they count towards the enemy goal....yes I know, stupid, isn't it? But there you have it...
Gamefaqs - Where you TOO can get an extra dose of textual diarrhea.