hmmmm
tough question.,
i cant give just 1 song as an answer..
so i'll list a bunch of powerfully emotional and moving songs...
:
in no order really...::
Little Mary
Meggie Sue
All I Ask
Paradise
Unsung
Annie
She Floats
Rinse
SuperHero
Twilight
Wanted
Afterglow (old&new lyrics)
well, these are the ones i noticed to be most 'powerful'