User blog comment:- Darkchylde/Acnologia's Element?/@comment-64.134.33.50-20151112175217

Water Dragon Slayer ,

Think about it for a moment... On Tenrou Island Acnologia absorbed water before he delivered the final blow that seemingly destroyed the island, Meaning he literally ate the water which leads me to believe he is the Water Dragon Slayer. Sure, Water might not be considered a powerful element.. But it's the counter to Fire (Of which natsu is the most powerful Fire user in the series.) Since Natsu is the most powerful Fire Protagonist then he needs an Antagonist Dragon Slayer who's the most powerful of their element to rival his own (which is water)