Dominique (the 15-year-old who runs around in nightclubs) doesn't have the worst design but I always hated the fact that she ran around in a jacket with no pants and a very weird hat. Looks like the precursor to a jester's hat.
Now Echidna is...she's supposed to be a security supervisor for this terrorist organization but I'm sorry she either looks like a street hooker or a bitchy sister of Waka from FFX.
Maybe I'm just a bit old-school but I like it when character designs infer something about the character. What in the fuck about Echidna's look says security or terrorist? Why is her hair so weird?
At least with Shalua, awful design that she was, you could infer that she was a scientist.