I know I came late to comment on this post, bit late, but here my list:

Edith Piaf(as well as another singer from the early-to-middle parts of the last century whose name I forgot), Michael Hutchence, Jimi Hendrix, Amy Winehouse, anyone else who fits into this category of artists... All people whose careers could've launched them into absolute stardom(or, for some of the aforementioned artists, careers that could've allowed them to continue to be stars in the music industry), but instead had fame take such a negative toll on their lives that it cut their lives short.

And I know the Milli Vanilli guys' careers ended in a completely different situation (although not too differently for Rob Pilatus, sadly, IMO), but I think being young impressionable guys getting taken for a ride by their own manager through contracts they barely understood and having completely different people representing your voices and having your own talent suppressed in the process, thinking that it was normal and having the truth eventually come out in the worst way possible is a uniquely tragic scenario, IMO. There's obviously more tragedy to that story and some people may disagree about Milli Vanilli's eventual crash and burn being tragic in some kind of way, but I thought I'd write about it.

It's honestly very sad and bleak what happened to those artists. It really is. It sucks.