Worst CELEBRATED writers?
Ayn Rand: She wrote endless, gushing, repetitive prose featuring one-dimensional characters, presented as rare moral paragons, paraded out in doorstop-length novels of pretentious political and economic drivel.
Ray Bradbury: Never wrote a sentence, let alone a story or novel, that didn't irritate me with its clumsy, moralizing self-importance. Moreover, his style overflows with metaphors that seem literary, until you think about them, and realize they evoke nothing. There's more to being a great writer than pioneering a niche genre.