From: Liquid Wind | #021
apparently either already knows something like the destructo disc or learns it from watching krillin do it.
i think he was already aware of the technique given that he knew enough to warn nappa to get out of the way. nappa had tanked everything prior to that but vegeta was aware that that technique would kill him. maybe he had seen freiza use it.
alternatively, he was simply a smarter fighter than nappa.
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