Those of us in the blogosphere sometimes take a perverse pride in our snarky put-downs. But we can't compare with writers slamming other writers. There is, for example, William Faulkner on Mark Twain:
A hack writer who would not have been considered fourth rate in Europe, who tricked out a few of the old proven sure fire literary skeletons with sufficient local color to intrigue the superficial and the lazy.
Hemingway accused Faulkner of drinking while he wrote. And Twain said of Jane Austen that every time he read "Pride and Prejudice" he wanted to dig her up and hit her over the skull with her own shinbone.
For elegance as well as venom, though, it's hard to beet Samuel Johnson on Milton's "Paradise Lost.":
'Paradise Lost' is one of the books which the reader admires and lays down, and forgets to take up again. None ever wished it longer than it is.