User blog comment:FairyRaven/Fairy Tail Chapter 400: Wings of Hope, Review and Commentary/@comment-24277053-20140913120858/@comment-7418318-20140913150043

But then why did he play around with the FT mages and then try to wipe them out?

Also if he had come for Zeref, he should have noticed Zeref's power being beside the island, not on it when Zeref killed Hades.

I suppose it's possible that he started out as you theorized, but at some point he must have given in to his growing bloodlust or somesuch. Though that would also be interesting in it's own right. He started out as the anti-hero, but turned into a tragic character more or less losing his mind. And in his attempt to save the world, he turned into a threat just as big as the one he tried to defeat.