I have a few that were extremely sad when it happened

Anna Nicole Smith
Dana Plato
Kobe Bryant
Owen Hart (Wrestler)
John Ritter
Robin Williams
Christopher Reeve
Eddie Guerrero (Wrestler)
Last year in January Lisa Marie Presley
Just last August was Brey Wyatt (Wrestler)

I really wanted to do this post because 2 I mentioned their 25th anniversary of their passing is approaching Dana Plato (5/8/99) and Owen Hart (5/23/99)

On your list, I felt pretty sad for:

Kobe Bryant
John Ritter
Robin Williams

I would have to say that the celebrity death that shocked me was Regis Philbin's because he seemed to be doing wonderful until I saw on Youtube that Regis Philbin had died at 88 and I was sure he would make it to his 89th birthday in 2020. He was talented and you can't find another guy like him in talk shows today

https://www.sitcomsonline.com/boards/showthread.php?t=248856&highlight=celebrity+death

For me it was John Denver. He died tragically and so young. I love his songs.

John Lennon
Karen Carpenter
Michael Jackson
George Michael
Prince
Erin Moran