Forum:Hard question

If I have the card Dark Cure already face up on the field when my opponent synchro summons One-Hundred Eye Dragon while Vennominaga the Deity of Poisonous Snakes is in the graveyard. My opponent only has 500 life points left. Would he lose? I know Dark Cure Implies that it targets, and even if it does, does the effect of Dark Cure resolve first.

Oh and Nurse Reficule the Fallen One is face up on the field, that's kinda important.