I think it could be about Sonny Liston, but the second verse and chorus, being so personal, makes me think it's more likely about a person Morrissey was close to, possibly a lover, whose life held parallels to the boxer's. I think Morrissey is using Sonny Liston's story to tell another, comparing a person to Sonny Liston. Also, the spelling is different, which may seem trivial, but Morrissey seems to notice these things.
I think it could be about Sonny Liston, but the second verse and chorus, being so personal, makes me think it's more likely about a person Morrissey was close to, possibly a lover, whose life held parallels to the boxer's. I think Morrissey is using Sonny Liston's story to tell another, comparing a person to Sonny Liston. Also, the spelling is different, which may seem trivial, but Morrissey seems to notice these things.