You haven't seen nothing yet!
You haven't seen anything yet! is the correct doublenegative in the given sentence.
A doublenegative is a sentence construction that employs two negative forms.
A double negative sentence is one in which two negative words or constructions cancel each other out, resulting in a positive meaning.
"I didn't see anything," for example, or "I can't find my keys anywhere." Both of these sentences contain two negative words that effectively create a positive meaning ("didn't" and "nothing" in the first sentence, and "can't" and "nowhere" in the second).
These sentences could be phrased more clearly as "I didn't see anything" and "I can't find my keys anywhere."
Thus, the doublenegative in the given sentence will be "You haven't seen anything yet!".
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