Board Thread:Manga/@comment-26624146-20170826063316/@comment-32563139-20170830093453

I wouldn't call Zeke the main antagonist of the story, he is definitely an antagonist, but but I think the real main villains are the Marley Government, or possibly the Tyber family when we get more information on them.

The main antagonist changes with each arc, The colossal titan for the first, then Annie for 'The Female Titan arc,' Reiner, Bertholdt and Zeke are kind of the antagonists in the 'Clash of the Titans arc' and the 'Return to Shinganshina arc,' Rod Reiss or even the MP's for the 'Uprising arc' and finally, the Marley Government  for the 'Marley arc'

So I don't think there will ever be a defined 'Main Antagonist' because there are different ones for each arc.