Board Thread:Show-Related Questions and Answers/@comment-34924658-20171113182231/@comment-1916997-20180131235423

Edzz wrote: Season 1: Main Antagonist: Regina Secondary Antagonist: Rumple Recurring Antagonists: Sidney, George Guest Antagonists: Cora, Maleficent, Jefferson, Blind Witch, Zoso

Season 2: Main Antagonists: Cora, Greg & Tamara Secondary Antagonists: Hook, Regina, Rumple Recurring Antagonists: George Guest Antagonists: Anita,  Maurice, Maleficent, Sheriff of Nottingham, Jack & James

Season 3: Main Antagonists: Peter Pan, Zelena Secondary Antagonists: Felix, the Shadow, Rumple (Under Zelena's control) Recurring Antagonists: Blackbeard Guest Antagonists: Greg & Tamara, Walsh

Season 4: Main Antagonists: Ingrid, and (Heavily up for debate but I'd say) Rumple Secondary Antagonists: Isaac, Cruella, Maleficent, Ursula, Zelena Recurring Antagonists: Charming & Snow (I'd classify their actions from 4x12-4x16 as antagonistic as well as their actions in the AU in 4x21-4x22), Sidney Glass, Hook (Under Rumple's control), Lily (Antagonistic in 4x19, 20 as well as in the AU) Guest Antagonists: Hans, Blackbeard, Duke of Weaselton, Bo Peep

Season 5: Main Antagonists: The Darkness (Again up for debate, but I'd say the Darkness is the impetus for Emma, Nimue and Hook's actions), Hades Secondary Antagonists: Emma, Zelena, Hook, Arthur, Nimue Recurring Antagonists: Cruella, Rumple, Peter Pan, James, Lord Macintosh, Blind Witch Guest Antagonists: Sir Kay, Vortigan, Captain Silver, Gaston, Hyde

​​​​​​​​​​​​​​Season 6: Main Antagonists: Evil Queen, Black Fairy Secondary Antagonists: Hyde, Gideon, ​​​​​​​​​​​​​​Recurring Antagonists: Jafar, Rumple, Zelena Guest Antagonists: Count of Monte Cristo, Lady Tremaine I, Jekyll, King George, Blackbeard

​​​​​​​​​​​​​​​​​​​​​Season 7 (thus far): Main Antagonists: (Again, very debateable) Drizella, Gothel Secondary Antagonists: Lady Tremaine II, Coven of the Eight ​​​​​​​​​​​​​​Recurring Antagonists:​​​​​​​ Dr Facillier ​​​​​​​ ​​​​​​​Guest Antagonists: The Prince

Looks like a pretty complete list to me.