Reversal in tragedies: a change from one state of affairs within the play to its opposite.

opposite

contradiction, countermand, opposition, recall, reversal, revocation

An about-face is an abrupt turn to face in the opposite direction, or a complete reversal of attitude, opinion or direction.

For men, a vasectomy is a procedure done to essentially sterilize a man and prevent reproduction. As such a vasectomy reversal is the opposite, allowing a male to potentially once again reproduce with a woman.