I wouldn't even call Axl Rose a singer!
Curiously, the lowest note for Freddie Mercury was a track he didn't sing lead vocal on, so I'm assuming they must have gone for backing vocals, but interesting that both his lowest and highest notes are on the same album,
News Of The World, and his highest note comes in perhaps Queen's greatest rock track,
It's Late.
Here you go, fight among yourselves. I would have put money on Jeff Buckley to lift the trophy (with, e.g. Grace), but what do I know.
An album I purchased after hearing the track
Hallelujah. I can't honestly say I've played it that much, but may dig it out now you've reminded me, Rod.