vs
Allure of Darkness
Card Text: Draw 2 cards, then banish 1 DARK monster from your hand, or, if you do not have any in your hand, send your entire hand to the GY.
Exodia the Forbidden One
Card Text: If you have “Right Leg of the Forbidden One”, “Left Leg of the Forbidden One”, “Right Arm of the Forbidden One” and “Left Arm of the Forbidden One” in addition to this card in your hand, you win the Duel.
The Verdict
Case 1: Player-A activates Allure of Darkness and subsequently draws the final piece of Exodia: Allure of Darkness must first complete its secondary (discard/banish) effect before Player-A is able to declare victory (assuming they still have all 5 pieces of Exodia in their hand).
WINNER = Allure of Darkness?
Further Resources
See the Exodia rulings here here.