From Longman Dictionary of Contemporary Englishthe villain of the piecethe villain of the piecethe person or thing that has caused all the trouble in a particular situation → villain
Examples from the Corpus
the villain of the piece• But to do so in this way was to make her appear the villain of the piece.• But who is really the villain of the piece?• Charles the Bald remained the villain of the piece.• Nor do I regard the villains of the piece as the fighters themselves. 