before you [one] can say “knife”
((略式))あっという間に,突然に
get [have, stick, put] one's knife into [in] A
((略式))A(人)をこきおろす
like a (hot) knife through butter
((英略式))すばやく;いとも簡単に
The knives are out (for A).
((略式))(A(人)にとって)とても険悪な雰囲気だ
twist [turn] the knife (in the wound)
いやなことに追いうちをかける,傷に塩を塗る
You [One] could cut the air [the atmosphere, it] with a knife.
非常に重々しい[険悪な]雰囲気だ