Actually, I don't think Day of the Dove is the one you were thinking of. Day of the Dove was nothing like that scene in Fifth Element.

When he said "the creature gained strength the more they fought" he didn't mean the more they fought the creature.

Ahhhh. And I do remember the ending where they decide to laugh. So it looks like I was maybe blurring the plot lines between reality (Star Trek) and science fiction (5th Element).