Well, at first I thought the topic title sounded harsh, like wishing harm to the people themselves, but after reading your post I realized what you were saying.
I grew up with Van Halen in my teen years. They turned into Van Hagar and bubblegum pop and sappy love songs, along with Aerosmith and the Scorpions. So those three are my "nominations".

Eh, Ill have to disagree there. I like some if the later stuff. Signals was a part of my golden years.

Another band that should have died was Def Leppard. High-N-Dry and then done.

Sometimes you have bands where the front man is such an iconic presence that replacement completely kills the mood. One of my favorite bands, The Tragically Hip, lost front man Gordon Downie last year. May that band rest in peace, while continuing to live on the memories of their past recordings.