Many people thought when they killed off Ned Stark, that Game of Thrones ratings would drop. He was arguably the most popular character and actor was beloved. Nevertheless they killed him off early and ratings have only increased. Part of GOT appeal is no one is safe even the main character(s).
Walking Dead has a similar appeal. However, honestly only Rick seems safe though. However, if they did kill off Rick would that turn off enough people from watching? I don't think so. However, I do think if they killed off Daryl ratings would be affected negatives. Similarly if they killed off say Daarey or Tyrion in GOT.
So are there any key deaths that would stop you from continuing to watch Walking Dead? Daryl? Carl? Rick? Glenn? Maggie? Judith? Etc.
I would be upset if Rick or Daryl bite the bullet, but I think I would still watch (unless the story just imploded)!
I would still watch the show no matter who bites the dust.
I would be most upset about Daryl and Rick, because I love their characters and your not expecting them to go. I hope Sasha and Tyreese make it a little longer, because I really like their characters.