Superlative form of whacky: most whacky.(adjective)
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Use "whackiest" in a sentence
"He enjoyed an absurd reputation as a moderate due to a biased, lazy press, when the truth is he often voted with the Inhofes and Coburns and the whackiest of the whacked."
"Even the wildest, craziest, whackiest scenario will get published if it is even within the realm of fantastic plausibility."
"One of the whackiest claims Sarah Palin makes in her new book is that she agreed to her disastrous interview with Katie Couric -- a ..."