How can you hate Blue? Yeah, she's tricky and stuff, but she has an interesting personality, sufficient character development, and breaks away from the standard stereotype of the Pokegirls. How many times in the series has Blue ever been the damsel in distress? Like, twice? Now how many times has she saved everyone else's butts? Let's see, there's the teleporting Silver away, bringing the legendary birds to battle Ho-Oh and Lugia, distracting Lorelei, defeating Lorelei when Sabrina was unconscious... Point is, Blue is an excellent character, and I can't imagine why anyone would dislike her.
But I digress. Anyway, my least favorite character would be Mitsumi from DPA(for all the reasons everyone else before me said) and Misty from PA. Nothing personal, though, it's just because she GETS IN THE WAY OF SPECIALSHIPPING GARRRRRRRRR. *rages*
PS: Am I the only one who actually likes the original characters in PA? Yellow is such a cutie and Emerald's Napoleon complex gets me every time <3