Mind the question tbh ;p this is not about how much you like their (band's) music or how much he did or changed in the world or music..but how much more he could have done

ps: Now go ahead and vote and moan about how useless or stupid this thread is, if you wish

pps: As the title said it's not about musicians before the 20th century, so as to not have to include people like Bach, Beethoven, Schönberg etc.

ppps: Yeah, my vote goes out to Cliff

For those who don't know: he was a (highly) classically influenced and brilliant metal bassist who died in a highly unfortunate accident while the band were touring for the 'Master of Puppets' album..
* Syd Barret: I know he's not dead! But something in him decided to leave and never return, rendering him incapable to do much more than one mediocre Pink Floyd album (showing his potential - and the rest of the band's - despite not being a remarkably original album as a whole) and two weird (but arguably brilliant) solo albums.