The term 'Banderillero Adversary' refers to a bullfighter in the sport of bullfighting. The banderillero is responsible for placing two barbed sticks, or banderillas, into the bull's shoulders during the fight. The adversary is the bull itself, which the banderillero must face in the ring. The crossword solution for this term is 'OLE', which is a Spanish word that is used to express approval or encouragement. It is often shouted by spectators during a bullfight to show their appreciation for the banderillero's skill and bravery.