I hoped that he would have become the villain of the show, ever since he first "rescued" Sansa. At the end of that season when it looks like Sansa may have found a way to manipulate him, followed immediately when he pawns her off to the Boltons at the very start of season 5 I thought "holy shit, he's always a step ahead of everyone". He always hid in the shadows and quietly pulled the puppet strings, but this season he's already managed to be caught out by Jon "I actually know everything" Snow.
Maybe he'll turn it around, but like Tyrion, Jaime and Cersei I worry that his story arc has ended and he's become nothing more than one dimensional.