The correct option is D success
The word 'fiasco' refers to a humiliating failure.
Option A, mess refers to a dirty or untidy state of things.
Option B, victory refers to an act of defeating an enemy.
Option C, fruitful refers to producing good and helpful results.
Option D, success refers to the accomplishment of an aim or purpose.
Thus, according to the meaning, the word 'success' is the opposite of the word 'fiasco'.