Thanks, TheQuiet1!
Now to add my own comment, I think it is probably U2's most universally powerful song. It is known by most people, and at many charity events, One is defintely going to be played. It was played at Live8 and and and at Hurricane Katrina. Universally, it reaches so many different people in so many different ways, the lyrics have been interpreted this way and that way, so it is probably their most universal song.
In terms of powerful, I'm less confident. In human terms, it is certainly powerful, because why would they play it at charity events otherwise? U2 mean business when they are doing One. But in song terms, I have to agree with The Quiet1. It certianly doesn't reach the elevated heights of other songs, and I think Where the Streets Have No Name could give One a run for its money in both categories.