Drop dead

In Breakfast of Champions, Kurt Vonnegut poised to kill Kilgore Trout, a character who showed up in many of his books as a stand-in for Vonnegut himself. But Vonnegut didn't kill Kilgore Trout. He said life, even fictional life, has value, and it isn't right to simply throw a life away for the sake of a story. 
Other authors don't share Vonnegut's view.
Agatha Christie hated Hercule Poirot. She called him a "detestable, bombastic, tiresome, ego-centric little creep." People loved Poirot, however, and so Christie was stuck with him. He appeared, according to Wikipedia, in 33 of her novels, one play, and over 50 short stories. In a case of art imitating life imitating art, she even had a recurring character in her novels called  Ariadne Oliver, a murder mystery author who hated her own famous creation, the fictional detective Sven Hjerson.

Yo, dog, we heard you like outdated memes.

Christie hated Poirot so much that she murdered him in 1945. That's when she wrote Curtain, in which Poirot dies from poisoning. She knew better than to release the story then - that detestable, bombastic little creep was a detestable, bombastic little cash cow for Christie. She only released the story a few months before her death in 1970. Poirot received a front page obituary in the New York times - the only obit for a fictional character they ever ran.

Sir Arthur Conan Doyle didn't wait so long to murder his greatest creation. From the start, Doyle thought that the Sherlock stories were beneath him. He had written other novels, novels he considered far better that the novels and short stories of the great Holmes, but it was Holmes his readers clamored for. Doyle killed off Holmes in 1893, saying "I have been much blamed for doing that gentleman to death, but I hold that it was not murder, but justifiable homicide in self-defense, since, if I had not killed him, he would certainly have killed me."
The readers would have none of that, and Sherlock came out of hiding ten years later, admitting he'd faked his own death. That wily bastard.

Poor Pooh. Not only is he a tubby idiot with a case of type II diabetes in his very near future, but his creator hated him. Milne was an author of books for grownups, and he didn't think much of the little stories he wrote for his son Christopher Robin. They were charming little vignettes that brought his son's toys to life... until they were published. That's when Milne went from accomplished author and playwright to that guy who writes about teddy bears. 
But Milne's hatred of Pooh was nothing compared to that of his son, who once said "It seemed to me almost that my father has got to where he was by climbing upon my infant shoulders, that he had filched from me my good name and had left me with the empty fame of being his son."
Funny - Milne didn't really like Pooh, wasn't particularly close to his son, and rather disliked children in general. And yet...

At least we can take solace in the fact that Milne didn't murder Pooh as far as we know... although he's probably on a collision course with a coronary pretty soon - if he doesn't die of stupid first.

Sources:
Wall Street Journal
The Popcultist
Express