I know I left out many. Don't chritisize that please. If your most hated character is not on the list ther is the "Other" option for you.
Most Helpful Girl
I actually like Ramsay. He's a bad man, certainly, but you can't deny that he's an interesting and well thought out character with a lot of depth to his personality. Viserys was a power-hungry, abusive asshole but I can understand what made him so dependent on the Throne - he was nothing without his birthright, the Iron Throne was his only means of a legacy and he truly did believe he was the one true king. In a way, I actually feel sorry for him. He sold his sister for an army and a crown, but his sister stole his spotlight. In his mind he deserved everything, but in the end he got nothing.
I don't really hate anyone to be honest, because it's hard to hate someone when the line between "good" and "evil" is so often crossed. But I do heavily dislike Theon. I never had any sympathy for him in the earlier seasons and I don't have any sympathy for him now as Reek. He lost all my respect when he torched Winterfell and lied about the deaths of Bran and Rickon.1