Updated the OP with a slightly better quality video.
But goddamn, I'm still blown away. Those ad-libs. Those inflections. Such a skilled vocalist, I live for this side of Christina. I'll continue to believe this until the end of my days - say what you say about her singing style, but her tone is one of the best of all time. So rich. Yes, I'm lovin' this performance that much.
I fail to see how this is oversinging, but opinions are opinions.
There's a difference between stanning for basic, limited and miniscule voiced singers and oversinging.
This is the sound of a gifted vocalist, powerhouse vocals that none of her peers can come close to. No reverb, over amped mics or echoes. The only stradivarius voice in the entire industry as of 2015