Reading Slash's comments on writing his stuff for Estranged is heartbreaking

[DeadSlash]

Use Your Illusion II's liner notes thank lead guitarist Slash for "the killer guitar melodies", which captured Axl Rose's vision. Slash has specifically stated that recording the guitar parts for this song was very intensive for him; he recorded it using a Les Paul Gold Top, using the rhythm pickup with the tone turned all the way down.^[1]

https://en.wikipedia.org/wiki/Estranged_%28song%29

Man, he really cared and put so much effort into helping bring to life the vision Axl had for the song. It really makes this line from Estranged hauntingly ironic;

I'll never find anyone to replace you

Guess I'll have to make it through, this time - oh this time

Without you

I think this is one of those things that proves how much they need each other. Axl had a vision for the song, and It's hard to disagree it was pretty damn good, and Slash was the only one that could pull it off. Neither of them does something this epic without the other.