Killed or missed opportunities, whatever... and ofcourse, it's my opinion and my truth and with respect, if one has other thoughts, please, then be it so.
To name some examples:

The Greatest Love Of All; this song has originally a beginning AND an end, the latter gives away the meaning of the song. It would have been great to have Shirley sing that statement with that magical voice of hers.

All the repertoire of Andrew Lloyd Webber, except for With One Look and As If We Never Said Goodbye, which are great for Shirley, for she can act out the lyrics.
Shirley's voice is simply not suited for that kind of songs.

Wild Is The Wind, such a beautiful and fantastic song for Shirley, but her intonation of the word Wild gives it a nasty edge.

I'm Still Here, because given it a half treatment to leave out the original lyrics by Stephen Sondheim. The man was not amused.

MacArthur Park, because it was so not Shirley's voice at all. It was an overproduced piece of work, due to bad production of Hello Like Before in its whole.

Maybe you can name some songs yourself?
I was always a critical admirer of Shirley Bassey's unbelievable talent and artistry...

I have never been 1000% fan of any artist that have come my way... to be-yes everything he or she does on record or stage is not my thing. But the 999% for me can do easily!

Shirley Bassey is part of my yesterdays, todays and tomorrows!