I accidentally voted Adele. Anyways Christina followed by Adele then Pink, after her Gaga from the poll. Lip synching makes the other girl not applicable to the word singer.

Xtina.

I don't consider Beyonce to be a powerhouse singer at all. Very thin vocals that don't can't carry emotional depth.

First of, emotion is subjective and irrelevant to this conversation. Bey doesn't sound like a fricking robat on stage so that argument is automatically invalid.
Second, her voice is definitely not thin and actually gotten darker and thicker due to age so that argument is also invalid.

Xtina and no one in that list comes close to her powerhouse vocals.
The woman sang LIVE for over an hr recently in New Orleans and slayed every "vocalist" from Bey to Pink.

Lol only on ATRL would Beyonce be winning over Xtina

Kelly, but Christina out of the ones you listed.