Board Thread:Spoilers!/@comment-1916997-20141224185559/@comment-26196542-20150312163815

Actually most of times, villains are resulting from other villains or stupid anti-heroes. Cora would never be a villain without Jonathan, and Rumple, and Eva is not quite a hero. Rumple is a result from Sozo and Hook. The only villain who seems to became villain by himself is Malcolm.

My theory about Ursula is that she fall in love with hook obviously manipulating her to get something. He says he did more than broke her heart, so maybe her innocence caused her fall and banishment from Atlantis.