It is very difficult for a QA team to fully test such a gigantic roster, so things like this happen in games. But has anybody else figured out the exploit that makes Chill invulnerable? (Kaos can still foot stomp directly on her for damage, as well as hit her with "the darkness" beam... unless I just haven't figured out the trick for them yet...)
Anyways, it totally breaks the game (and PVP), but if you want to pursue making Chill invulnerable to each type of enemy in the game here is a hint:
It has a lot to do with positioning to maintain it. Standing still is just a part of it.
I just cake walked over Mesmerelda on Nightmare for my 'no damage' third star in story mode, and I only stood in two places on the board. I still need to get the third star on Kaos' Mom and Kaos himself. (round 2 of Kaos' Mom is difficult to trick the positions when the healer(s) drop, and Kaos just requires a lot of patience)
I had to go back and check Giants for the same exploit, but it doesn't exist in the last game

-Goose